By Karen Price
Endorsed by Science Alliance for Forestry Transformation (SAFT)1
Studies of habitat thresholds have been used to estimate the risk to biodiversity and ecological function in BC,2 Canada3 and elsewhere.4 Thresholds are built into reports describing planetary change.5 The literature examining habitat thresholds has grown considerably in the 15 years since the approach was first applied in BC.6 This summary updates evidence for habitat thresholds, describes considerations for using thresholds to guide conservation and compares the existing approach used in BC to published literature.
What are habitat thresholds?
Ecological thresholds are points of rapid change (also called “tipping points” or “regime shifts”) in ecological condition in response to small changes in external factors.7 Extensive experimental, observational and modelling evidence supports the occurrence of ecological thresholds in a variety of ecosystems.8
Habitat thresholds are a sub-set of ecological thresholds, identifying a habitat amount (where habitat is defined at an appropriate scale and ecosystem type for a species) associated with rapid changes in biodiversity (e.g., species richness), population size (e.g., extinction, abundance), or behaviour (e.g., patch occupancy, pollination).9 Habitat amount influences landscape pattern; as amount declines, patches of suitable habitat become smaller and/or further apart.10 When studies tease apart the effects of amount and pattern, habitat amount matters most.11
Why do habitat thresholds matter?
Habitat loss is the principal factor driving the global biodiversity crisis, as populations decline towards extirpation.12 Habitat thresholds can indicate points of irreversible change.13 In turn, biodiversity loss impacts ecosystem function and services (e.g., productivity, decomposition, pollination, disease spread, resilience).14 Species, and combinations of species, play complementary roles in stabilising ecosystem function through disturbance and under variable conditions; species loss can destabilise function.15
Habitat thresholds matter for forest management and conservation because they provide guidance about where small changes in habitat amount may lead to important ecological change.16
Evidence for habitat thresholds
Studies agree that habitat thresholds are common in diverse species and regions around the globe.17 While most studies focus on birds, habitat thresholds have been documented in mammals, amphibians, invertebrates and plants.18 Unsurprisingly, there is no single “magic” threshold; threshold amount varies widely by study, species and region, with factors including life history (e.g., habitat specialists have higher thresholds than generalists), dispersal ability, scale, type of threshold (e.g., reproductive, population, community) and landscape context (e.g., high quality matrix habitat mitigates habitat loss; forest degradation causes population declines even with constant total amount).19 Relevant to BC’s forest management, old forest specialists will be more sensitive to loss of old growth than either generalists or young forest specialists.20
Sufficient evidence for habitat thresholds existed in the early 1990s to allow a meta-analysis of more than 30 studies, which found that most thresholds, where detected, occurred between 10 and 30% habitat.21 This is the first well-cited paper that summarises evidence across species and communities for increased risk below 30% habitat. As statistical methodology and data availability improved, and projects considered larger spatial and temporal scales, subsequent studies found thresholds at higher habitat amounts, with many occurring between 30% and 60% habitat, and some above 70%.22
Studies of probability of extinction at different habitat levels provide additional evidence that retaining 30% of habitat threatens persistence of some species (e.g., 13/25 bird species have below a 50% probability of persistence with 30% habitat, 8/25 with 50% habitat and 3/25 with 70% habitat).23 In the tropics, conserving 30% of the area reduces combined probability of extinction across thousands of species by 50%; conserving 50% of the area reduces extinction probability by more than 70%.24
As well as empirical studies, modeling studies offer guidance. For example, in modeled landscapes, habitat patches start to separate from each other at about 60% of a landscape, and become fully fragmented below 30%,25 suggesting thresholds in landscape structure at 30% and 60%.26
Studies of stand-level retention find similar thresholds to those documented at the landscape scale. For example, forest bird communities in stands with low retention (about 20%) change, while those in stands with high retention (above 40 – 60%) are similar to those in mature forest.27 Similar patterns exist in bryophytes and late-successional plants.28 Soil communities are similar to unharvested stands at above 60 – 70% retention, and decline below 50% retention.29
Several lines of evidence suggest that some habitat thresholds may be higher than detected. First, poorly-studied organisms, apex predators and rare species may experience thresholds at higher habitat amounts than the birds and small mammals studied most often.30 Unfortunately, the most sensitive species may be hardest to study, and some may already be lost.31 Second, studies rarely consider long- enough time periods to capture time lags (“extinction debt”) in response to habitat loss.32 Third, thresholds in species richness are extreme measures, representing the endpoint of many extirpations; they may be difficult to detect because generalist species may compensate for the loss of specialists.33
Using habitat thresholds to guide forest management and conservation
Because quantitative targets for representing ecosystems underpin planning,34 habitat thresholds have long been recognised as an important management tool.35 Targets informed by thresholds have been implemented in a range of contexts, including forest management and restoration.36 Caution is required to ensure that thresholds are applied to appropriate, representative ecosystems (i.e., “forest cover” is insufficient as a metric; thresholds must apply to different forest ecosystems).37
Most approaches define a minimum habitat amount that avoids high risk to biodiversity within representative ecosystems. The evidence for high risk below 30% habitat is sufficiently incontrovertible that it inspired a global agreement for 30% conservation of representative ecosystems by 2030.38 Thirty percent, however, is insufficient to maintain all species: evidence for higher thresholds, up to at least 70% (see above), coupled with uncertainty, has led to concerns about choosing a single target percent.39 Natural disturbances continue in retained old forest, meaning that realised habitat decreases over time. Setting targets based on extinction thresholds will not ensure persistence over time: managing to the high-risk precipice is a dangerous strategy.40
Options to address uncertainty include using precaution (i.e., setting higher targets), gathering more data or defining a range of risk with associated probabilities.
To address evidence for higher thresholds, and uncertainty, a recent meta-analysis suggests retaining 40% as a minimum,41 with higher areas in the tropics.42 At the stand scale, biodiversity-friendly coffee certification uses the same threshold, requiring 40% canopy cover.43 Several efforts have suggested that 50% of the earth should be conserved to ensure maintenance of biodiversity and ecosystem services on which we depend.44
Gathering more data
The variability in thresholds and concern that higher thresholds remain undetected has led to suggestions that thresholds should be regionally-defined for sensitive local species.45 Unfortunately, while choosing regionally relevant targets might be ideal, the current crisis precludes the time for such research.46 Management that ignores evidence due to variability and uncertainty risks damage and irreversible consequences.47 Threshold science does not claim that a single value explains all patterns, but identifies reasonably consistent levels where risk to biodiversity is higher.48
Trying to capture the variation and uncertainty in thresholds has led to a more flexible probability-based approach that defines a region between low- and high-risk limits.49 Meeting global conservation goals likely requires conserving somewhere between 25 – 75% of land and water.50
In BC51 and Canada,52 planning processes have used a risk curve, where risk to biodiversity is defined as the probability of crossing a habitat threshold (Figure 1). In this approach, risk is likely low with more than 70% of habitat remaining (i.e., low probability that species cross a threshold) and likely high with less than 30% remaining. Uncertainty is higher between these points, where risk will depend on species traits and landscape condition. The probability approach mirrors that used by the IPCC to define the likelihood of climate impacts.53
Figure 1. Habitat risk curve, based on studies of habitat thresholds and used in BC. Risk to biodiversity is likely low when more than 70% habitat remains, likely high when less than 30% remains, and less certain between.
Development of a planetary boundary framework uses a risk approach conceptually identical to that used in BC (Figure 2).54 For a variety of factors, including biodiversity, climate change, land-use change and biochemical flows, the framework defines points for low- and high- risk, with uncertainty between, thus suggesting a “safe operating space”. This safe operating space varies across factors: the biosphere integrity index suggests biodiversity intactness should be from 30 – 90% of pre-industrial values; the land-use change index (based on impacts to climate) suggests a range of 54 – 75% of original forest cover.55
Figure 2. Copied from Fig. 1 in Steffen et al. 2015.56 Showing a risk curve for planetary boundaries with areas of safe operating space (green), uncertainty (yellow) and high risk (red).
Recent evidence confirms that the approach used in BC to estimate risk to biodiversity (Figure 1) remains consistent with the best-available knowledge. The need to maintain more than 30% of representative ecosystems is incontrovertible; low-risk above 70% is less certain, but consistent with knowledge. This approach will be particularly useful if the province moves towards prioritising ecological integrity in forest management.57
Even when uncertainty prevents precise threshold location, awareness of the risks of crossing thresholds has led to cooperation elsewhere, in climate negotiations and avoidance of thresholds by resource extractors.58 Multiple lines of evidence, including empirical studies, modelling studies, and traditional knowledge can reduce uncertainty, but residual uncertainty is unavoidable.59 The approach used in BC captures uncertainty, allows flexibility in decision-making based on the acceptable level of risk, and can easily be updated as knowledge increases.60
Notes and References
1 Including forest ecologists Jim Pojar, Phil Burton, Rachel Holt, Dave Daust, Andy MacKinnon, Suzanne Simard, Dave Coates, Frank Doyle, Len Vanderstar and others.
2 Price, K., Holt, R. F., & Daust, D. (2021). Conflicting portrayals of remaining old growth: the British Columbia case. Canadian Journal of Forest Research, 51(5), 742-752. Price, K., Roburn, A., & MacKinnon, A. (2009). Ecosystem-based management in the Great Bear Rainforest. Forest Ecology and Management, 258(4), 495-503.
3 Environment Canada, 2013. How much Habitat is Enough? third ed. Environment Canada, Toronto, Ontario. McAfee, B.J., Malouin, C., 2008. Implementing Ecosystem-Based Management Approaches in Canada’s Forests. A Science-Policy Dialogue. Natural Resources Canada, Canadian Forest Service, Headquarters, Science and Programs Branch, Ottawa. Ontario Nature, 2004. Suggested Conservation Guidelines for the Identification of Significant Woodlands in Southern Ontario. Federation of Ontario Naturalists, Toronto, Ontario.
4 Foley, M. M., Martone, R. G., Fox, M. D., Kappel, C. V., Mease, L. A., Erickson, A. L., Halpern, B. S., Selkoe, K. A., Taylor, P., & Scarborough, C. (2015). Using ecological thresholds to inform resource management: Current options and future possibilities. Frontiers in Marine Science, 2, 95. https://doi.org/10.3389/fmars.2015.00095. Kelly RP, Erickson AL, Mease LA, Battista W, Kittinger JN, Fujita R. 2015. Embracing thresholds for better environmental management. Philos. Trans. R. Soc. B. 370(1659):20130276. Dodds WK, Clements WH, Gido K, Hilderbrand RH, King RS. 2010. Thresholds, breakpoints, and nonlinearity in freshwaters as related to management. J. North Am. Benthol. Soc. 29(3):988–97.
5 Intergovernmental Platform on Biodiversity and Ecosystem Services; Diaz S, Settele J, Brondizio ES,Ngo HT, Agard J, et al. 2019. Pervasive human-driven decline of life on Earth points to the need for transformative change. Science 366(6471):1–10
6 About 30 peer-reviewed papers per year use the term “ecological threshold” in the past decade. Shennan‐Farpón, Y., Visconti, P., & Norris, K. (2021). Detecting ecological thresholds for biodiversity in tropical forests: Knowledge gaps and future directions. Biotropica, 53(5), 1276-1289.
7 Spake, R., Barajas-Barbosa, M. P., Blowes, S. A., Bowler, D. E., Callaghan, C. T., Garbowski, M., ... & Chase, J. M. (2022). Detecting thresholds of ecological change in the Anthropocene. Annual Review of Environment and Resources, 47. Huggett, A. J. (2005). The concept and utility of ‘ecological thresholds’ in biodiversity conservation. Biological conservation, 124(3), 301-310. Groffman, P. M., Baron, J. S., Blett, T., Gold, A. J., Goodman, I., Gunderson, L. H., ... & Wiens, J. (2006). Ecological thresholds: the key to successful environmental management or an important concept with no practical application? Ecosystems, 9, 1-13.
8 Biggs, R. O., Peterson, G. D. & Rocha, J. C. C. (2018) The Regime Shifts Database: a framework for analyzing regime shifts in social-ecological systems. Ecol. Soc. 23, 9. Diaz, R. J. & Rosenberg, R. (2008) Spreading dead zones and consequences for marine ecosystems. Science 321, 926–929. Walker, B. & Meyers, J. A. (2004). Thresholds in ecological and social–ecological systems: a developing database. Ecol. Soc. 9, 3 (2004)., Hirota, M., Holmgren, M., Van Nes, E. H. & Scheffer, M. (2011). Global resilience of tropical forest and savanna to critical transitions. Science 334, 232–235. Spake et al. (2022) see note 7. Scheffer, M. et al. (2015). Creating a safe operating space for iconic ecosystems. Science 347, 1317–1319. Newbold, T., Tittensor, D. P., Harfoot, M. B. J., Scharlemann, J. P. W., & Purves, D. W. (2018). Non-linear changes in modelled terrestrial ecosystems subjected to perturbations. BioRxiv, 439059. https:// doi.org/10.1101/439059. Steffen, W., Richardson, K., Rockström, J., Cornell, S. E., Fetzer, I., Bennett, E. M., ... & Sörlin, S. (2015). Planetary boundaries: Guiding human development on a changing planet. Science, 347(6223), 1259855.
9 For example: Arroyo-Rodríguez, V., Fahrig, L., Tabarelli, M., Watling, J. I., Tischendorf, L., Benchimol, M., Cazetta, E., Faria, D., Leal, I. R., Melo, F. P. L., Morante-Filho, J. C., Santos, B. A., Arasa-Gisbert, R., Arce-Peña, N., Cervantes-López, M. J., Cudney-Valenzuela, S., Galán-Acedo, C., San-José, M., Vieira, I. C. G., … Tscharntke, T. (2020). Designing optimal human-modified landscapes for forest biodiversity conservation. Ecology Letters, 23(9), 1404–1420. https://doi.org/10.1111/ ele.13535. Banks-Leite, C., Pardini, R., Tambosi, L. R., Pearse, W. D., Bueno, A. A., Bruscagin, R. T., Condez, T. H., Dixo, M., Igari, A. T., Martensen, A. C., & Metzger, J. P. (2014). Using ecological thresholds to evaluate the costs and benefits of set-asides in a biodiversity hotspot. Science, 345(6200), 1041–1045. https://doi.org/10.1126/scien ce.1255768. de Oliveira Roque, F., Menezes, J. F. S., Northfield, T., Ochoa-Quintero, J. M., Campbell, M. J., & Laurance, W. F. (2018). Warning signals of biodiversity collapse across gradients of tropical forest loss. Scientific Reports, 8(1), 1622. https://doi.org/10.1038/s41598-018- 19985-9. Melo, I., Ochoa-Quintero, J. M., Oliveira Roque, F., & Dalsgaard, B. (2018). A review of threshold responses of birds to landscape changes across the world. Journal of Field Ornithology, 89(4), 303– 314. https://doi.org/10.1111/jofo.12272. Lindenmayer, D. B., & Luck, G. (2005). Synthesis: thresholds in conservation and management. Biological Conservation, 124(3), 351-354. Ficetola, G., & Denoel, M. (2009). Ecological thresholds: An assessment of methods to identify abrupt changes in species-habitat relationships. Ecography, 32(6), 1075–1084. https://doi. org/10.1111/j.1600-0587.2009.05571.x.
10 Fahrig, L. (2003). Effects of habitat fragmentation on biodiversity. Annual review of ecology, evolution, and systematics, 34(1), 487-515.Fahrig, L. (2017). Ecological Responses to Habitat Fragmentation Per Se. Annual Review of Ecology, Evolution and Systematics 48, 1–23
11 There is agreement that amount matters most: fragmentation influences populations in some regions and some levels of habitat; effects can be positive or negative. Fahrig 2017 (see Note 10). De Camargo, R. X., Boucher‐Lalonde, V., & Currie, D. J. (2018). At the landscape level, birds respond strongly to habitat amount but weakly to fragmentation. Diversity and Distributions, 24(5), 629-639. Pardini, R. et al. 2010. Beyond the fragmentation threshold hypothesis: regime shifts in biodiversity across fragmented landscapes. PLoS ONE 5, e13666. Villard, M.-A. & Metzger, J. P. 2014. Beyond the fragmentation debate: a conceptual model to predict when habitat configuration really matters. J. Appl. Ecol. 51, 309–318.
12 Jaureguiberry, P., Titeux, N., Wiemers, M., Bowler, D. E., Coscieme, L., Golden, A. S., ... & Purvis, A. (2022). The direct drivers of recent global anthropogenic biodiversity loss. Science advances, 8(45), eabm9982. Pereira, H. M., Navarro, L. M., & Martins, I. S. (2012). Global biodiversity change: the bad, the good, and the unknown. Annual Review of Environment and Resources, 37, 25-50.
13 Mönkkönen, M. and Reunanan, P. 1999. On critical thresholds in landscape connectivity: a management perspective. Oikos 84:302-305.
14 Syntheses in Cardinale, B.J., Duffy, J.E., Gonzalez, A., Hooper, D.U., Perrings, C., Venail, P., 568 Narwani, A., Mace, G.M., Tilman, D., Wardle, D.A., Kinzig, A.P., Daily, G.C., Loreau, M., Grace, J.B., Larigauderie, A., Srivastava, D.S., Naeem, S., 2012. Biodiversity loss and its impact on humanity. Nature 486, 59-67. Naeem, S., Duffy, J.E., Zavaleta, E. 2012. The functions of biological diversity in an age of extinction. Science 336, 1401-1406. Hooper, D. U. et al. (2012) A global synthesis reveals biodiversity loss as a major driver of ecosystem change. Nature 486, 105–108. Bonfim, F. C. G., Dodonov, P., Guimarães Jr, P. R., & Cazetta, E. (2022). Habitat loss shapes the structure and species roles in tropical plant–frugivore networks. Oikos, e09399. Estavillo, C., Pardini, R., & da Rocha, P. L. B. (2013). Forest loss and the biodiversity threshold: An evaluation considering species habitat requirements and the use of matrix habitats. PLoS One, 8(12), e82369. https://doi.org/10.1371/journal.pone.0082369. Suzán G, Marcé E, Giermakowski JT, Mills JN, Ceballos G et al. (2009) Experimental Evidence for Reduced Rodent Diversity Causing Increased Hantavirus Prevalence. PLOS ONE 4(5): e5461. doi:https://doi.org/10.1371/journal.pone.0005461. Stenseth NC, Leirs H, Skonhoft A, Davis SA, Pech RP et al. (2003) Mice, rats, and people: the bio-economics of agricultural rodent pests. Front Ecol Environ 1: 367–375. doi:10.1890/1540-9295(2003)001[0367:MRAPTB]2.0.CO;2.Vidal, M. M., Banks‐Leite, C., Tambosi, L. R., Hasui, É., Develey, P. F., Silva, W. R., ... & Metzger, J. P. (2019). Predicting the non‐linear collapse of plant–frugivore networks due to habitat loss. Ecography, 42(10), 1765-1776. Briske, D.D., Fuhlendorf, S.D., Smeins, F.E., 2006. A unified framework for assessment and application of ecological thresholds. Rangeland Ecology and Management 59, 561 225-236. Suding, K.N., Hobbs, R.J. 2009. Threshold models in restoration and conservation: a developing framework. Trends in Ecology and Evolution 24, 271–279.
15 Reviewed in Gonzalez, A., Loreau, M. 2009. The causes and consequences of compensatory dynamics in ecological communities. Annual Review of Ecology, Evolution, and Systematics 40, 393-414. Francesco Ficetola, G., & Denoel, M. (2009). Ecological thresholds: An assessment of methods to identify abrupt changes in species-habitat relationships. Ecography, 32(6), 1075–1084. https://doi. org/10.1111/j.1600-0587.2009.05571.x. Mori, A.S., Furukawa, T., Sasaki, T. 2013. Response diversity determines the resilience of ecosystems to environmental change. Biological Reviews 88, 349–364.
16 See Note 9.
17 Andrén, H. (1994). Effects of habitat fragmentation on birds and mammals in landscapes with different proportions of suitable habitat: A review. Oikos, 71(3), 355–366. Gutzwiller, K. J., Riffell, S. K., & Flather, C. H. (2015). Avian abundance thresholds, human-altered landscapes, and the challenge of assemblage-level conservation. Landscape Ecology, 30, 2095-2110. Swift, T. L., & Hannon, S. J. (2010). Critical thresholds associated with habitat loss: a review of the concepts, evidence, and applications. Biological reviews, 85(1), 35-53. Zuckerberg, B., & Porter, W. F. (2010). Thresholds in the long-term responses of breeding birds to forest cover and fragmentation. Biological Conservation, 143(4), 952-962.
18 For example, Homan, R.N., Windmiller, B.S., and Reed, J.M. 2004. Critical thresholds associated with habitat loss for two vernal pool-breeding amphibians. Ecological Applications 14:1547-1553. Gibbs, J.P. 1998. Distribution of woodland amphibians along a forest fragmentation gradient. Landscape Ecology 13:263-268. Lennartsson, T. 2002. Extinction thresholds and disrupted plant-pollinator interactions in fragmented plant populations. Ecology 83: 3060-3072. Reunanen, P., Mönkkönen, M., Nikula, A., Hurme, E. and Nivala, V. 2004. Assessing landscape thresholds for the Siberian flying squirrel. Ecological Bulletins 41:277-286. Summerville, K.S. and Crist, T.O. 2001. Effects of experimental habitat fragmentation on patch use by butterflies and skippers (Lepidoptera). Ecology 82:1360-1370. Tscharntke, T., Steffan-Dewenter, I., Kruess, A., and Thies, C. 2002. Contribution of small habitat fragments to conservation of insect communities of grassland-cropland landscapes. Ecological Applications 12:354-363. Virgós, E. 2001. Role of isolation and habitat quality in shaping species abundance: a test with badgers (Meles meles L.) in a gradient of forest fragmentation. Journal of Biogeography 28:381-389. Bascompte, J. and Rodriguez, M.A. 2001 Habitat patchiness and plant species richness. Ecology Letters 4:417-420. Gonzalez, A. and Chaneton, E.J. 2002. Heterotroph species extinction, abundance and biomass dynamics in an experimentally fragmented microecosystem. Journal of Animal Ecology 71:594-602. Hargis, C.D., Bissonette, J.A. and Turner, D.L. 1999. The influence of forest fragmentation and landscape pattern on American martens. Journal of Applied Ecology 36:157-172. Siira-Pietikäinen, A., & Haimi, J. (2009). Changes in soil fauna 10 years after forest harvestings: Comparison between clear felling and green-tree retention methods. Forest Ecology and Management, 258(3), 332-338.
19 Lisón, F., Matus-Olivares, C., Troncoso, E., Catalán, G., & Jiménez-Franco, M. V. (2022). Effect of forest landscapes composition and configuration on bird community and its functional traits in a hotspot of biodiversity of Chile. Journal for Nature Conservation, 68, 126227. Pardini, R. et al. 2010. Beyond the fragmentation threshold hypothesis: regime shifts in biodiversity across fragmented landscapes. PLoS ONE 5, e13666. Estavillo, C., Pardini, R., & da Rocha, P. L. B. (2013). Forest loss and the biodiversity threshold: An evaluation considering species habitat requirements and the use of matrix habitats. PLoS One, 8(12), e82369. https://doi.org/10.1371/journal.pone.0082369. Morante-Filho, J. C., Benchimol, M., & Faria, D. (2021). Landscape composition is the strongest determinant of bird occupancy patterns in tropical forest patches. Landscape Ecology, 36, 105-117. Ramírez-Delgado, J.P., Di Marco, M., Watson, J.E.M. et al. 2022. Matrix condition mediates the effects of habitat fragmentation on species extinction risk. Nat Commun 13, 595. https://doi.org/10.1038/s41467-022-28270-3. Price, K., Daust, K., Lilles, E., & Roberts, A. M. (2020). Long-term response of forest bird communities to retention forestry in northern temperate coniferous forests. Forest Ecology and Management, 462, 117982. Tscharntke T, Klein AM, Kruess A, Steffan-Dewenter I, Thies C (2005) Landscape perspectives on agricultural intensification and biodiversity-ecosystem service management. Ecol Lett 8: 857–874. doi:https://doi.org/10.1111/j.1461-0248.2005.00782.x.Betts, M. G., Yang, Z., Hadley, A. S., Smith, A. C., Rousseau, J. S., Northrup, J. M., ... & Gerber, B. D. (2022). Forest degradation drives widespread avian habitat and population declines. Nature Ecology & Evolution, 6(6), 709-719. Newbold, T., Hudson, L.N., Phillips, H.R.P., Hill, S.L.L., Contu, S., Lysenko, I. et al. (2014). A global model of the response of tropical and sub-tropical forest biodiversity to anthropogenic pressures. Proc. R. Soc. B., 281, 20141371. Swihart RK, Lusk JJ, Duchamp JE, Rizkalla CE, Moore JE (2006) The roles of landscape context, niche breadth, and range boundaries in predicting species responses to habitat alteration. Divers Distrib 12: 277–287. doi:https://doi.org/10.1111/j.1366-9516.2006.00242.x.
20 Price, K., Daust, K., Lilles, E., & Roberts, A. M. (2020). Long-term response of forest bird communities to retention forestry in northern temperate coniferous forests. Forest Ecology and Management, 462, 117982. Price, K., Lilles, E. B., & Banner, A. (2017). Long-term recovery of epiphytic communities in the Great Bear Rainforest of coastal British Columbia. Forest Ecology and Management, 391, 296-308. Radies, D. N., & Coxson, D. S. (2004). Macrolichen colonization on 120–140-year-old Tsuga heterophylla in wet temperate rainforests of central-interior British Columbia: a comparison of lichen response to even-aged versus old-growth stand structures. The Lichenologist, 36(3-4), 235-247.
21 Andrén, H. (1994). (See Note 17)
22 For example, 30 – 40% for boreal and temperate forest birds with large ranges: Rompré, G., Boucher, Y., Bélanger, L., Côté, S., & Robinson, W. D. (2010). Conserving biodiversity in managed forest landscapes: The use of critical thresholds for habitat. The Forestry Chronicle, 86(5), 589– 596. https://doi.org/10.5558/tfc86589-5; average of 48% across tropics (with region and study as random variable, meta-analysis): Shennan‐Farpón, Y., Visconti, P., & Norris, K. (2021). Detecting ecological thresholds for biodiversity in tropical forests: Knowledge gaps and future directions. Biotropica, 53(5), 1276-1289; 61% average persistence threshold for temperate breeding birds over 20 years at large scales: Zuckerberg, B., & Porter, W. F. (2010). Thresholds in the long-term responses of breeding birds to forest cover and fragmentation. Biological Conservation, 143(4), 952-962.; above 70% for African bird species: Kupsch, D., Vendras, E., Ocampo-Ariza, C., Batáry, P., Motombi, F. N., Bobo, K. S., & Waltert, M. (2019). High critical forest habitat thresholds of native bird communities in Afrotropical agroforestry landscapes. Biological Conservation, 230, 20-28. Average 70% for persistence: van der Hoek, Y., Renfrew, R., Manne, L.L., 2013. Assessing regional and interspecific variation in threshold responses of forest breeding birds through broad scale analyses. PLoS One 8, e55996; 80% for full occupancy Chilean forest birds: Vargas-Cárdenas, F., Arroyo-Rodríguez, V., Morante-Filho, J. C., Schondube, J. E., Auliz-Ortiz, D. M., & Ceccon, E. (2022). Landscape forest loss decreases bird diversity with strong negative impacts on forest species in a mountain region. Perspectives in Ecology and Conservation, 20(4), 386-393.
23 van der Hoek, Y., Zuckerberg, B., & Manne, L. L. (2015). Application of habitat thresholds in conservation: Considerations, limitations, and future directions. Global Ecology and Conservation, 3, 736–743. https://doi.org/10.1016/J.GECCO.2015.03.010.
24 Hannah, L., Roehrdanz, P. R., Marquet, P. A., Enquist, B. J., Midgley, G., Foden, W., ... & Svenning, J. C. (2020). 30% land conservation and climate action reduces tropical extinction risk by more than 50%. Ecography, 43(7), 943-953.
25 Fahrig 2003, Andrén, H. (1994). (See Note 17), Pardini et al. 2010, Roque, F. de O. et al. 2018. Warning signals of biodiversity collapse across gradients of tropical forest loss. – Sci. Rep. 8: 1622.
26 Desmet, P. G. (2018). Using landscape fragmentation thresholds to determine ecological process targets in systematic conservation plans. Biological Conservation, 221, 257-260.
27 Caudill, S. A., & Rice, R. A. (2016). Do bird Friendly® coffee criteria benefit mammals? Assessment of mammal diversity in Chiapas, Mexico. PLoS One, 11(11), e0165662. https://doi.org/10.1371/ journal.pone.0165662. Price et al. (2020). (See Note 20). Tittler, R., Hannon, S. J., & Norton, M. R. (2001). Residual tree retention ameliorates short‐term effects of clear‐cutting on some boreal songbirds. Ecological Applications, 11(6), 1656-1666. Harrison, R. B., Schmiegelow, F. K., & Naidoo, R. (2005). Stand-level response of breeding forest songbirds to multiple levels of partial-cut harvest in four boreal forest types. Canadian Journal of Forest Research, 35(7), 1553-1567. Le Blanc, M. L., Fortin, D., Darveau, M., & Ruel, J. C. (2010). Short term response of small mammals and forest birds to silvicultural practices differing in tree retention in irregular boreal forests. Ecoscience, 17(3), 334-342. Otto, C. R., & Roloff, G. J. (2012). Songbird response to green-tree retention prescriptions in clearcut forests. Forest Ecology and Management, 284, 241-250. Fenton, N. J., Imbeau, L., Work, T., Jacobs, J., Bescond, H., Drapeau, P., & Bergeron, Y. (2013). Lessons learned from 12 years of ecological research on partial cuts in black spruce forests of northwestern Québec. The Forestry Chronicle, 89(3), 350-359. Beese, W. J., Arnott, J. T., Baker, S. C., Bancroft, B., Benton, R. A., Blackwell, B. A., ... & Camps, Y. S. (2013). Variable retention harvesting in north Pacific temperate rainforests.
28 Reviewed in Rosenvald, R., & Lõhmus, A. (2008). For what, when, and where is green-tree retention better than clear-cutting? A review of the biodiversity aspects. Forest Ecology and Management, 255(1), 1-15.
29 Reviewed in Prescott, C. E., & Grayston, S. J. (2023). TAMM review: Continuous root forestry—Living roots sustain the belowground ecosystem and soil carbon in managed forests. Forest Ecology and Management, 532, 120848.
30 Shennan‐Farpón, Y., Visconti, P., & Norris, K. (2021). Detecting ecological thresholds for biodiversity in tropical forests: Knowledge gaps and future directions. Biotropica, 53(5), 1276-1289.
31 Betts, M. G. et al. 2017. Global forest loss disproportionately erodes biodiversity in intact landscapes. Nature 547, 441-444.
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37 Lindenmayer, D. B., & Luck, G. (2005). Synthesis: thresholds in conservation and management. Biological Conservation, 124(3), 351-354.
38 Convention on Biological Diversity COP15 2022. Kunming-Montreal Global Biodiversity Framework. https://www.cbd.int/article/cop15-cbd-press-release-final-19dec2022 Dinerstein, E., Vynne, C., Sala, E., Joshi, A. R., Fernando, S., Lovejoy, T. E., ... & Wikramanayake, E. (2019). A global deal for nature: guiding principles, milestones, and targets. Science advances, 5(4), eaaw2869.
39 Lindenmayer, D. B., & Luck, G. (2005). Synthesis: thresholds in conservation and management. Biological Conservation, 124(3), 351-354.
40 Desmet, P. G. (2018). (See Note 26). Arroyo-Rodriguez et al. (2020) (See Note 9)
41 Arroyo-Rodriguez et al. (2020) (See Note 9)
42 Shennan-Farpon et al. (2021) (See Note 30)
43 Caudill, S. A., & Rice, R. A. (2016). Do bird Friendly® coffee criteria benefit mammals? Assessment of mammal diversity in Chiapas, Mexico. PLoS One, 11(11), e0165662. https://doi.org/10.1371/ journal.pone.0165662
44 Dinerstein, E., D. Olson, A. Joshi, C. Vynne, N. D. Burgess, E. Wikramanayake, N. Hahn, S. Palminteri, P. Hedao, R. Noss, M. Hansen, H. Locke, E. C. Ellis, B. Jones, C. V. Barber, R. Hayes, C. Kormos, V. Martin, E. Crist, W. Sechrest, L. Price, J. E. M. Baillie, D. Weeden, K. Suckling, C. Davis, N. Sizer, R. Moore, D. Thau, T. Birch, P. Potapov, S. Turubanova, A. Tyukavina, N. de Souza, L. Pintea, J. C. Brito, O. A. Llewellyn, A. G. Miller, A. Patzelt, S. A. Ghazanfar, J. Timberlake, H. Klöser, Y. Shennan-Farpon, R. Kindt, J.-P. B. Lillesø, P. van Breugel, L. Graudal, M. Voge, K. F. Al-Shammari, M. Saleem, 2017. An ecoregion-based approach to protecting half the terrestrial realm. Bioscience 67, 534–545. R. F. Noss, A. P. Dobson, R. Baldwin, P. Beier, C. R. Davis, D. A. Dellasala, J. Francis, H. Locke, K. Nowak, R. Lopez, C. Reining, S. C. Trombulak, G. Tabor. 2012. Bolder thinking for conservation. Conserv. Biol. 26, 1–4. E. O. Wilson 2016. Half Earth: Our Planet’s Fight for Life (Liveright Publishing Corporation, ed. 1). E. Sala, K. Rechberger 2018. in From Summits to Solutions: Innovations in Implementing the Sustainable Development Goals, R. Desai, H. Kato, H. Kharas, J. McArhur, Eds. (Brookings Institution Press), pp. 239–261. Dinerstein, E., Vynne, C., Sala, E., Joshi, A. R., Fernando, S., Lovejoy, T. E., ... & Wikramanayake, E. (2019). A global deal for nature: guiding principles, milestones, and targets. Science advances, 5(4), eaaw2869.
45 Banks-Leite, C., Larrosa, C., Carrasco, L. R., Tambosi, L. R., & MilnerGulland, E. J. (2021). The suggestion that landscapes should contain 40% of forest cover lacks evidence and is problematic. Ecology Letters, 24(5), 1112–1113. https://doi.org/10.1111/ele.13668
46 Arroyo-Rodriguez et al. (2020) (See Note 9); Desmet, P. G. (2018). (See Note 26). Lade SJ, Wang-Erlandsson L, Staal A, Rocha JC. 2021. Empirical pressure-response relations can benefit assessment of safe operating spaces. Nat. Ecol. Evol. 5:1078–79.
47 Peterson, G. D., Carpenter, S. R. & Brock, W. A. 2003. Uncertainty and the management of multistate ecosystems: an apparently rational route to collapse. Ecology 84, 1403–1411 (2003).
48 Arroyo‐Rodríguez, V., Fahrig, L., Watling, J. I., Nowakowski, J., Tabarelli, M., Tischendorf, L., ... & Tscharntke, T. (2021). Preserving 40% forest cover is a valuable and well‐supported conservation guideline: reply to Banks‐Leite et al. Ecology Letters, 24(5), 1114-1116. Spake et al. (2022) see note 7.
49 Steffen, W., Richardson, K., Rockström, J., Cornell, S. E., Fetzer, I., Bennett, E. M., ... & Sörlin, S. (2015). Planetary boundaries: Guiding human development on a changing planet. Science, 347(6223), 1259855. Desmet, P. G. (2018). (See Note 26).
50 R. F. Noss, A. P. Dobson, R. Baldwin, P. Beier, C. R. Davis, D. A. Dellasala, J. Francis, H. Locke, K. Nowak, R. Lopez, C. Reining, S. C. Trombulak, G. Tabor, 2012. Bolder thinking for conservation. Conserv. Biol. 26, 1–4. R. L. Pressey, R. M. Cowling, M. Rouget, 2003. Formulating conservation targets for biodiversity pattern and process in the Cape Floristic Region, South Africa. Biol. Conserv. 112, 99–127. 22. B. C. O’Leary, M. Winther-Janson, J. M. Bainbridge, J. Aitken, J. P. Hawkins, C. M. Roberts 2016, Effective coverage targets for ocean protection. Conserv. Lett. 9, 398–404. Dinerstein, E., Vynne, C., Sala, E., Joshi, A. R., Fernando, S., Lovejoy, T. E., ... &
Wikramanayake, E. (2019). A global deal for nature: guiding principles, milestones, and targets. Science advances, 5(4), eaaw2869.
51 Price, K., Holt, R. F., & Daust, D. (2021). Conflicting portrayals of remaining old growth: the British Columbia case. Canadian Journal of Forest Research, 51(5), 742-752. Price, K., Roburn, A., & MacKinnon, A. (2009). Ecosystem-based management in the Great Bear Rainforest. Forest Ecology and Management, 258(4), 495-503. Gorley, A and Merkel G. 2020. A new future for old forests. https://www2.gov.bc.ca/gov/content/industry/forestry/managing-our-forest-resources/old-growth-forests/strategic-review-of-old-growth-forest-management
52 Environment Canada, 2013. How much Habitat is Enough? third ed. Environment Canada, Toronto, Ontario. McAfee, B.J., Malouin, C., 2008. Implementing Ecosystem-Based Management Approaches in Canada’s Forests. A Science-Policy Dialogue. Natural Resources Canada, Canadian Forest Service, Headquarters, Science and Programs Branch, Ottawa. Ontario Nature, 2004. Suggested Conservation Guidelines for the Identification of Significant Woodlands in Southern Ontario. Federation of Ontario Naturalists, Toronto, Ontario.
53 Mastrandrea, M.D., Field, C.B., Stocker, T.F., Edenhofer, O., Ebi, K.L., Frame, D.J., Held, H., Kriegler, E., Mach, K.J., Matschoss, P.R. and Plattner, G.K., 2010. Guidance note for lead authors of the IPCC fifth assessment report on consistent treatment of uncertainties.
54 Steffen, W., Richardson, K., Rockström, J., Cornell, S. E., Fetzer, I., Bennett, E. M., ... & Sörlin, S. (2015). Planetary boundaries: Guiding human development on a changing planet. Science, 347(6223), 1259855. Rockström, J., Steffen, W., Noone, K. et al. 2009. A safe operating space for humanity. Nature 461, 472–475. https://doi.org/10.1038/461472a. Running 2012, Mace et al. 2014
55 Steffen et al. (2015). (see Note 54). Scholes, R. J., & Biggs, R. (2005). A biodiversity intactness index. Nature, 434(7029), 45-49. These estimates are for global processes, summarising impacts at regional scales, and considering interactions amongst factors.
56 Steffen et al. (2015). (see Note 54).
57 Gorley, A and Merkel G. 2020. A new future for old forests. https://www2.gov.bc.ca/gov/content/industry/forestry/managing-our-forest-resources/old-growth-forests/strategic-review-of-old-growth-forest-management
58 Lade, S. J., Wang-Erlandsson, L., Staal, A., & Rocha, J. C. (2021). Empirical pressure-response relations can benefit assessment of safe operating spaces. Nature Ecology & Evolution, 5(8), 1078-1079. Rocha, J. C., Schill, C., Saavedra-Díaz, L. M., Del Pilar Moreno, R. & Maldonado, J. H. (2020). Cooperation in the face of thresholds, risk, and uncertainty: experimental evidence in fisher communities from Colombia. PLoS ONE 15, e0242363. Barrett, S. & Dannenberg, A. (2012). Climate negotiations under scientific uncertainty. Proc. Natl Acad. Sci. USA 109, 17372–17376 (2012).
59 Lade et al. (2021). (See Note 58).
60 Price, K., & Daust, D. (2009). Making monitoring manageable: a framework to guide learning. Canadian journal of forest research, 39(10), 1881-1892.
Rachel Holt presents Old Growth Forests: What is the path forward? to alumni of UBC’s Faculty of Forestry.
In her presentation, Holt refers to a critique produced by Veridian Ecological in response to COFI’s claim (through a study authored by forester Cam Brown) that 29.3 percent of all old forest in the province has a site index greater than 20 metres. You can read that response here.
In the section on “Jobs” in her UBC presentation, Holt refers to the “number of jobs per cubic metre.” She doubtless meant to say the “number of jobs per thousand cubic metres”. An excellent analysis of what the big issues are right now regarding continued logging of old-growth forests and the logging industry’s denialism.
Following Holt’s and Brown’s presentations at UBC, they got together to uncover common ground. Holt wrote a short paper outlining that common ground. This is also useful in understanding the issues around the amount of remaining old growth. You can read that paper here.
Managing Northern Goshawks and many of our other larger animal species that depend on old forests will not be achieved simply by old growth deferral of the most at-risk old forests. It is critical that we quickly move beyond the deferrals to the ultimate goal of effective landscape planning, with ecologically appropriate targets for forest retention at the core.
Review of the remaining known active Northern Goshawk territories in the Skeena Region indicates that:
• Although helping to support the nesting and foraging requirements of Northern Goshawks, old growth deferrals as being proposed will be insufficient to maintain the population or the viability of individual territories.
• However, if these now scattered and often disjunct old growth deferral areas were strategically designated within the remaining contiguous large tracts of forest—including the more productive valley bottoms—they could immediately provide very effective habitat cornerstones supporting the needs of Northern Goshawks, and a wide range of other focal old growth species.
Lessons learned from 25 years of monitoring and research on Northern Goshawks in B.C.
In west central B.C., there has been a precipitous decline in the population of Northern Goshawks as a direct result of clearcut logging (rate and extent of cut), and subsequent conversion of primary forests to short-rotation tree plantations. Northern Goshawks are year-round residents of our forest landscapes, where they are the apex avian predator within old forests. These large hawks are adapted to hunt beneath the canopy of these forests, where from hidden perches they ambush. They rely on fully functioning, older forest ecosystems, to provide the diversity and abundance of food they require (squirrels, grouse, hares, forest songbirds, etc.). They were once common in the region; now instead of thousands of pairs, we have a few hundred. Because their breeding areas and core foraging home ranges are usually located at lower elevations, nearly all known and “still occupied” territories are threatened by additional planned timber harvest. Logging to date has forced regional Northern Goshawk populations to the to the brink of viability, and we now must focus management on maintaining the remaining viable territories.
Northern Goshawk Habitat Needs
Species such as Northern Goshawks that evolved in old growth-dominated forest landscapes need mature and old growth forest to survive and thrive.
Like the vast majority of our forest birds and mammals, pairs of Northern Goshawks are territorial, and historically distributed themselves evenly across the forested landscape. The birds forage in the forest around their nests, and radio telemetry/GPS tracking studies have shown how the size of this foraging home range fluctuates through the year, according to prey abundance and habitat. They are year-round residents in their territories, and to breed they need sufficient food to survive the winter, sufficient food for the female to form and lay eggs in April, and sufficient food in spring and summer for the birds to reside and raise the young in their foraging home range.
Through the collective work in our landscapes, we now understand that a goshawk’s breeding area is a fixture in the landscape, and the birds will use the same specific area for generations of birds. The size of the breeding area is governed by habitat competition and nest territoriality with other goshawks in the landscape. As such, by visiting these sites, biologists know very clearly how many birds there are, and how well they are responding to changes in their home range area. When the breeding area is excessively logged or burned, the birds do not seek other territory (already abandoned due to forest modification or presently occupied), resulting in further territorial abandonment. In fact, approximately 90% of the 150 known Northern Goshawk breeding areas within the Skeena Region are now quiet and are, or soon will be, abandoned. Unless we change how we manage our forests, we will never see the return of this species to historic breeding areas, and will further witness their extirpation across landscapes.
In the Skeena Region, breeding pairs are spaced regularly every 4-6 km in old-growth forests. This pattern and the validating research using radio telemetry show that in summer Northern Goshawk breeding home areas range from 2,400 to 4,000 ha, and in winter this expands to an area 2 or more times as large (3,000 – 8,000 ha). Within a breeding area, habitat analysis shows that on average ~75% of the forest cover is composed of mature and old-growth stands. This ~75% requirement for mature and old growth is an average. Many territories will fail before the ~75% level is reached, and nearly all will fail if we manage for just the lowest level (~60%) observed for an active territory in our region.
Northern Goshawk Habitat Management Challenge
Forests at a landscape scale (think Northern Goshawk home range area; several 1,000s ha), are a vast tapestry of several different tree species, stand types and ages, and myriad site types (understory vegetation, patchiness, wetlands, landforms, slope aspects, moisture status, etc.). This biophysical complexity affects the overall abundance of the birds and other animals within any given area. Given this complexity and the availability of prey species for Northern Goshawks, there is no definable home range boundary that we can determine prior to timber harvesting (i.e., we cannot identify a habitat threshold for each territory that will ensure that the birds will have enough food). Each territory threshold is unique and could vary year to year.
Chillingly, for many species requiring larger tracts of older forest, habitat management is now about deciding which species and in what abundance we want to occupy our forested landscapes. Planning for these species will fail if left to chance, minimum thresholds, or deregulated resource industries and depopulated management agencies.
Rising to the Management Challenge:
Currently in the Skeena Region a team of biologists and foresters, in partnership with government, forest licensees and First Nations, are responding to the above findings. The focus is on developing Tactical Plans to maintain a viable long-term Northern Goshawk population, through the management of probable and known individual territories across given landscapes.
Integral to this approach is the integrated stewardship direction laid out by the BC Minister in "Together for Wildlife Strategy" (Doug Donaldson 20 August 2020, https://engage.gov.bc.ca/wildlifeandhabitat/), and the Forest Practices Board identified need for wildlife management to be built around a Tactical Plan (FPB. July 2019. Tactical Forest Planning: The Missing Link Between Strategic Planning and Operational Planning in BC. https://www.bcfpb.ca/reports-publications/reports/tactical-forest-planning-the-missing-link-between-strategic-planning-and-operational-planning-in-bc/).
At all scales, these long-term tactical plans must focus on the retention of the old growth structure that supports the requirements of Northern Goshawks and their prey (and of course apropos today’s Climate Change headlines - this same structural retention will help mitigate flooding, rising stream temperatures, and greenhouse gas emissions). In B.C. we have a wealth of forest research, and we already know what combination of forest retention, timber harvest and post-harvest silvicultural techniques can deliver appropriate stewardship for Northern Goshawks while still allowing for timber extraction.
Not surprisingly, maintaining habitat for the large home range needs of Northern Goshawk also supports the habitat needs of many other forest dwelling wildlife species, including Fisher, Marten, Wolverine, Grizzly Bear, Moose, Caribou, Spotted Owl among others.
Fundamentally, stewardship of many of these species requires a new and long overdue approach to management of our forested landscapes, addressing the need for large unfragmented areas as cornerstones to wildlife species management. The ongoing discussion regarding old growth deferrals sets the stage for revitalized land use planning, and is a stepping-stone to ensuring support for keystone species such as the Northern Goshawk. Strategic placement of deferrals within the already mapped ~200 suitable Northern Goshawk territories in the Skeena Region could quickly provide the initial outcome that is urgently needed, as outlined in the integrated stewardship direction identified in the “Together for Wildlife Strategy”. Northern Goshawks and many other old growth dependent species are relying on us.
This article in PDF format: 2021-12 Old Growth Forests & Species Management.pdf
OVER THE PAST THREE DECADES, forest sector employment has decreased by about half, from about 100,000 jobs in 1991-1999 to about 50,000 in 2010-2018 (1). Various factors have been proposed as responsible for this loss including mechanisation, loss of accessible fibre, increased wildfire and beetle disturbance, increased raw log export, increased area in protection, etc. It’s possible to use federal statistics to tease apart some of these factors. If increased protection, increased natural disturbance or loss of accessible timber were responsible for most of the job loss, the volume and/or area harvested would decrease. However, if increased mechanisation and/or raw log export were responsible, the jobs would decrease while volume and area harvested remained stable (i.e., jobs per unit volume would decrease).
Although the volume harvested per year has fluctuated somewhat (with a drop around the 2008-2009 recession), volume per decade has remained relatively constant at about 70 million cubic metres over the past three decades. Volume harvested has decreased somewhat in the last decade, about 10% from the 1990s and 2000s, partly due to decreased cut post-beetle and partly due to regional shortages of accessible, merchantable fibre (and subsequent mill closures). This small drop contrasts strongly with the larger drop in the number of jobs per volume. The number of jobs per unit volume harvested has dropped from an average of 1.3 jobs per thousand cubic metres in the 1990s to three quarters of a job per thousand cubic metres from 2010-2018:
Figure 1. Jobs per 1000 cubic metres
This decline in jobs per unit volume suggests that mechanisation, and perhaps raw log exports, are responsible for most of the loss rather than decreased area available for harvest due to protection, loss of fibre or increased disturbance (which would reduce volume harvested not jobs per volume).
Properly quantifying the effects of mechanisation and log exports on job loss requires accounting for the effects of volume harvested. Using the jobs/cubic metre average for the 1990s as a baseline (1.3 jobs per thousand cubic metres) and projecting expected jobs forward from 2000 to 2018 based on the volume harvested per year estimates that 25,000 jobs were lost to mechanisation and perhaps raw log export by the 2000s and 38,000 jobs were lost by the 2010s (lost jobs calculated as the average difference between projected jobs and actual jobs over the decade in Figure 2).
Figure 2. Jobs projected based on annual volume harvested and jobs per cubic metre values (1.3 jobs/thousand cubic metres 1990s baseline) compared to actual jobs. The blue line represents the maximum jobs in the past three decades.
From a high of about 100,000 jobs, decreased volume was only responsible for a large part of decreased jobs during the 2008-2009 recession (compare the dotted line to the blue horizontal line); a decrease in jobs per unit volume was responsible for most of the job loss. This change was likely due primarily to increased efficiency in mills and increased mechanisation of harvest. Analyses done elsewhere suggest an annual loss of 3,600 jobs due to raw log export (2).
Increased natural disturbance may reduce volume available for harvest, contributing to job loss. Natural disturbances are salvaged where possible. The increased volume harvested around 2005 was due to uplifts in AACs for mountain pine beetle salvage.
Wildfires burned 3.5 million hectares of forest in the past decade, about half in the THLB. While much of the merchantable THLB may be salvaged, some will be inaccessible and some volume will be lost to char. If a quarter of disturbed THLB area cannot be salvaged, for example, fires will remove about 21,000 hectares of harvestable timber per year based on trends over the last decade. Assuming the current jobs per hectare (0.75 jobs per cubic metre) and stocking of 350 cubic metres per hectare, wildfires can be inferred to be responsible for a loss of 5,500 jobs each year.
(1) Forestry and logging, pulp and paper manufacturing, wood product manufacturing and support activities for forestry; https://cfs.nrcan.gc.ca/statsprofile/employment/BC. Survey of employment, payrolls and hours. Data are publicly available from 1991 – 2018 for most factors.
This article in PDF format: 2021-10 Job Change in the Forest Sector.pdf
Len Vanderstar’s Review, June 1, 2021
My comments below are based on a review of the Intentions Paper released on June 1, 2021. Given that what was presented today by the province is an intentions document, by default it is not binding at this time, so my comments must take this into account. Without getting too deep into the subject matter and from my perspective, I have listed pros/semi-pros & cons associated with the provincial government’s intentions with respect to modernizing forest policy.
• Reaffirms government’s commitment to UNDRIP, however the Declaration on the Rights of Indigenous Peoples Act already applies to B.C. laws, but implementation delay remains problematic with respect to an action plan and progress report.
• Increasing opportunity for new entrants in the forest sector, thus possibly supporting diversity and small business.
• Forest tenure re-distribution and revising tenure disposition considerations, with the intent to increase indigenous replaceable forest tenure opportunity and local community forest tenure options.
• Re-affirmation of implementing the recommendations from the Old Growth Strategic Review Report (Gorley-Merkel), however one of the key recommendations of an immediate moratorium on @ risk old-growth has been misapplied based on manipulative false data.
• Improvement of FRPA – tactical planning approach to better consider forest values with up- front Indigenous involvement, and re-instituting Statutory Decision Maker authority to reject a cutting or road permit based on resource stewardship concerns... “could irreparably impair other forest values”.
• Beginning to recognize a need for transition from maximizing timber volume to optimizing product value.
• Advance a process to minimize the burning of slash piles and freeing up fibre for product manufacturing, although no mention was made of minimizing the creation of slash.
• Increasing penalties for poor practices and behaviour with the intent to increase the deterrent.
• Forest tenure holders to be held accountable to harvest profiles expressed in the AAC to avoid the continuous of preferential stand harvest.
• Re-integration of prescribed fire into forest management with a focus on wildfire mitigation and habitat creation.
• Some very vague language that I am interpreting, but requires clarification, to actually base the AAC on growth & yield plots rather than hypothetical model growth projections... “consider limits on timber harvest until provincial silviculture investments have optimal harvest opportunity in consideration of risk and other values.”
• Unabated logging of valued old-growth forests remains an ongoing concern; legitimate concern still exists with the talk and log scenario.
• Seemingly lack of recognition of the biodiversity crisis recognition in our forests; no forest structure & function management direction, although the commitment to implementing the Old Growth Strategic Review recommendations is mentioned, and one of the recommendations speaks to prioritizing ecosystem health and resiliency.
• No recognition that AACs must be reduced to prevent further loss/extirpation of forest dependent species.
• No mention of science-based factual data or core foundation advice to drive informed decision making. This is a major concern for the Science Alliance for Forestry Transformation. Where are the independent scientists?
• Compensation for lost harvesting rights may not translate to actual loss of volume of logs being transported to mills currently holding forest tenures, so public fund compensation should be carefully administered.
• Lack of commitment to reduce whole log export, just ability to audit fee-in-lieu of manufacturing (this was not being done before?). Four to five million m3/yr. of whole log export greatly reduces domestic employment and associated personal income tax to government.
• Re-distribution of tenure without acknowledging the first step to ensure adequate forest protection/conservation may result in an ineffective roll-out.
2021-06 Modernizing Forest Policy in BC - Comments by Len Vanderstar.pdf
British Columbia Forest Policy Reforms Needed for Sustainability
By Karen Price, Rachel Holt, Dave Daust, Phil Burton, Jim Pojar, Dave Coates, Jay Gilden, Len Vanderstar
BRITISH COLUMBIA’S forest management policies urgently require reform to sustain ecosystems and communities, and to help address the current climate and biodiversity crises. Priorities include:
1) revised land use plans that protect more primary forest,
2) more realistic timber supply analyses, and
3) reformed forest tenures that better reflect community needs.
B.C.’s forests, particularly productive old growth, are critical for mitigating climate change and maintaining biodiversity. Retaining carbon-dense old forests is a very effective natural climate solution, key to meeting 2050 emissions targets. Old growth resists wildfire, ameliorates flooding and drought, reduces temperature, and provides climate refugia. B.C. bears a global responsibility for biodiversity and carbon sequestration because of its globally rare, productive, coastal and inland temperate rainforests. Increased retention also addresses Canada’s commitment to protect 30% of representative ecosystems by 2030. Retention priorities were not adequately implemented following land-use planning in the 1990s, largely due to provincial policies that continued to favour industrial timber interests.
B.C.’s timber supply is declining and rural communities face crisis. Supply fall-downs have been anticipated for decades, but ignored by successive governments. Optimistic timber supply models, that underestimate the effects of disturbance and a changing climate, have contributed to unsustainable harvest rates, biodiversity declines and community instability. Additionally, preferential harvest of productive sites has left lower volume and higher cost stands, exposing mills to closures. Timber supply projections must include current science on growth rates, mortality, and climate change, and must partition harvest by productivity.
Over recent decades, forest jobs in B.C. have declined as a few large corporate players—including provincially-managed B.C. Timber Sales—dominate management, converting an inherited supply of old growth forest to short-term economic benefit. A forest tenure system that gives oversight to forest-based communities may better support Indigenous rights and sustain multiple ecological and social values.
This article in PDF format: 2021-05 Abstract submission for 2021 Commonwealth Forestry Conferences.pdf
Science Alliance for Forestry Transformation: Who are we?
We are scientists and applied science forest professionals with expertise and experience in terrestrial and riparian ecology, biodiversity, wildlife, disturbance dynamics, forestry, climate change, land-use planning, risk assessment, cumulative effects, resilience and landscape analysis (including timber supply). We are not social scientists or economists. We have worked on collaborative land-use planning around the province and are intimately familiar with barriers to success as well as potential pathways through the gauntlet of vested interests to the greater public interest.
Our big ask: reform forest management to sustain ecosystems and communities
Update land use planning, with an increased emphasis on protection of primary and old-growth forests;
Adjust timber harvesting levels, supported by more realistic determinations of allowable annual cuts to promote sustainable forestry practices;
Reform forest tenure, with greater community and indigenous control of forest management to increase social, environmental and economic resilience.
Approach: base decisions on science and acceptable risk
Forest management often ignores or obfuscates science that conflicts with short-term economic objectives, thus threatening ecosystem and community sustainability.
Sufficient scientific knowledge does not exist within the ministry. A changing baseline, poor institutional memory, continuance of business-area silos, innumeracy, senior bureaucrats with limited vision, and naïve young staff lacking mentors mean that lessons are lost and issues remain unresolved. A culture of “getting to yes” means that problems are swept under the rug.
Splitting the ministry provides the opportunity to introduce science-based decision-making, for example via a Chief Ecologist/Scientist and Independent Scientific Panels. Land-use planning provides opportunities to prioritize goals that bring long-term benefits to society, biodiversity and climate. Incorporating science in planning is critical to ensuring that management strategies work towards the goals.
Context: climate and biodiversity crises
We live in a time of unprecedented global crisis: the climate is almost out of control (1), we are participating in a great extinction event (2), and our societal systems have increased human vulnerability (3). At the same time, a social awakening to inequality and push for change led by youth provides an opportunity to act (4).
The set of suggestions outlined below follow in the wake of our “Big Ask” as critical action items to address the climate and biodiversity crises.
Challenge: legal and policy direction prioritizes timber
BC’s existing land-use plans have been, for the most part, ignored. As planning moves through the system, public intent is lost because industry speaks loudest. Many consensus objectives remain in the non-legal realm and subject to professional reliance…which has failed: rather than meeting intent, implementation aims to extract the most resources. Existing plans are out-dated, excluding climate change, new resource activities, and current science; many lack substantive First Nations’ engagement (5).
Suggestion: use land-use planning to retain more old growth forest
BC’s primary forests (6), particularly productive old growth ecosystems, are critical for mitigating climate change, adapting to climate change and maintaining biodiversity and ecological integrity. Land-use planning provides a mechanism for considering the well-documented importance of old forest and improving management accordingly.
Old forests store vast amounts of carbon (7). Retaining carbon-dense old forest is the most effective natural climate solution, far superior to planting trees, and critical to meeting 2050 emissions targets designed to prevent catastrophic change. Ecosystems with infrequent disturbance that grow large trees (i.e., coastal and inland temperate rainforest) are most important to protect.
Harvesting old forests releases carbon (8). From 40 – 66% of carbon is lost to the atmosphere after harvest. More is lost through processing, meaning that “long-lived wood products” store a quarter or less of the carbon in a standing forest. Harvesting forests for bioenergy emits more carbon than using fossil fuel sources.
Replacing old forests with young does not recover stores (9). It takes 100 to > 250 years to recover the stored carbon after logging; shorter rotation (<80 years) managed stands never recover the carbon of a natural forest. Carbon sequestration cannot replace carbon stores.
Old growth resists wildfire and flooding (10). Despite increased biomass, old growth burns less, due to buffered air temperature, stored moisture and structure that resists wildfire. Hydrology changes following harvest. Harvested stands are more vulnerable to the changed precipitation patterns, including intense storm events and droughts driven by climate change.
Intact primary forests maintain biodiversity and provide a suite of ecosystem services (11). These forests are critical for biodiversity, ecological integrity and services people need and care about.
Old growth provides wildlife habitat. Intact forest at multiple scales supports population growth and dispersal and provides climate refugia.
Intact forest buffers water flow and temperature. Forests act as sponges, releasing water slowly to buffer extreme low flows. They also shade streams from increased air temperature, protecting sensitive fish.
Works towards international protected area agreements and federal commitments to 30% by 2030. Currently BC is not meeting agreements to protect 17% of representative terrestrial ecosystems.
BC has a global responsibility for biodiversity and carbon, particularly because of its rare and productive coastal and inland temperate rainforests.
Implements the Old Growth Panel recommendations as specified in mandate letter.
Addresses multiple foundational principles and directives in mandate letters.
Supporting actions to increase forest protection include the following:
Shift paradigm from timber to ecological integrity (i.e., implement Old Growth Panel recommendation #2);
Change legal requirements to remove “without unduly impacting timber supply” clause (i.e., complete FRPA update #2).
Implement Old Growth Panel recommendations in their entirety;
Update carbon accounting to properly value storage in old forest as compared with validated managed stand contributions;
Increase conservation and wildlife habitat protection in land use plans;
Conservation science knows how much of each representative ecosystem to retain in order to have a high probability of maintaining ecological function.
Empower First Nations to develop interim moratoria on timber harvest in their traditional territories to evaluate ecological and cultural values, and ensure collaboration.
Emphasize long-term sustainability for communities by shifting the reliance on limited primary forest that will be gone within a decade.
Land-use planning provides the regional-scale mechanism to increase protection of primary forest. Here are a few models.
Omineca Environmental Stewardship Initiative. Carrier Sekani First Nations and the Province have mapped biodiversity management areas for conservation. These agreed-upon areas should have been included in the government’s deferral areas.
Gitanyow Land Use Plan. This plan, which increased conservation for biodiversity, cultural values and water management, has been incorporated into legal objectives. Gitanyow asked the province to decrease the AAC on their territory because modeling shows it is not sustainable from an economic perspective (let alone ecological). The province has not yet agreed.
Great Bear Rainforest. Many complexities here. A better process and targets than most other plans, but implementation remains a challenge as industry still high-grades the biggest trees.
Clayoquot Sound Scientific Panel. The province’s first collaborative science/traditional ecological knowledge panel with recommendations accepted by the province.
Increase in-stand retention to increase the probability of maintaining biodiversity and ecosystem function.
Addresses biodiversity, climate mitigation, refugia, wildlife, water protection
The science is well developed, with regional examples (e.g., Date Creek Research Forest in Kispiox Valley)
Increase diversity in tree species to address uncertainty and climate change.
Challenge: optimistic models overestimate timber supply
BC’s timber supply has reached its fall-down and rural communities are in crisis. Using optimistic models to set allowable annual cut levels has driven forest management in perverse directions, leading to over-harvest, community instability and biodiversity declines. Growth and yield models have overestimated stand growth, by underestimating the effects of natural disturbances and ignoring climate change. This optimism, coupled with a lack of monitoring and operational scale model validation that could have corrected course, has led to unsustainable harvest rates.
In many parts of BC, little old growth remains available for harvest. This timber supply fall-down has been anticipated for decades, but not addressed. Because harvest focused on productive stands, what remains often has low volumes and high costs, which exposed many BC mills to collapse and shutdown when lumber prices fell in 2019. A long-term future for communities can only be based on diverse rural economies that meet the global demand for low-carbon products rather than focusing on high-carbon resource extraction.
Suggestion: develop a realistic annual allowable cut
A realistic allowable annual cut (AAC) is a prerequisite for a strong sustainable economy, for environmental sustainability, for reconciliation and for fighting climate change.
Use a realistic approach to model timber supply that includes current science on growth rates, disturbance and mortality. Update models based on improved inventory and extensive monitoring of stand health and growth.
Account for climate change in models. Future tree mortality will increase due to increased drought, wildfire and storm disturbance, insect outbreaks and pathogens.
Expand inventory to validate and calibrate models. Base harvest levels on inventory and monitoring rather than uncertain forecasts.
Ensure that high productivity sites are not preferentially harvested; do not leave only high-cost, low-value forests for future generations.
Quebec forestry has changed from using simulation models to set AAC (as BC does now) to using inventory plots to monitor growth rates and help set AAC level. This seems to be a positive change.
Gitanyow Hereditary Chiefs have conducted an independent timber supply review on their territory that considers the best knowledge about mortality and growth, and incorporates climate impacts. The methods estimate the probability of different harvest levels being sustainable and allow determination of a sustainable AAC based on risk tolerance. To date, the province is considering their input, but has not changed the AAC.
Challenge: short-term economics vs. resource-dependent communities
The industrial status-quo threatens rural communities. Many rural communities in BC depend upon resource extraction for jobs. Over recent decades, many mills have closed and forest jobs have declined as large corporate industry works to maximize short-term profit and invest profits in mills elsewhere while liquidating BC’s old growth.
The current model puts industrial timber economics above local economies and employment as well as above community health (e.g., clean water, clean air, recreation and spiritual experiences). Foresters face a conflict of interest when managing forest tenures directly tied to mills that are linked to corporations and shareholders.
Economic and productive systems need to be transformed to power the shift to sustainability.
Suggestion: tenure reform
Reform the forest tenure system to reduce emphasis on an oligopoly of multinational corporations and place control in collaborative organizations that embrace sustainability and indigenous rights. For example, regional forest trusts and community governance bodies can determine important values (such as ecological sustainability, clean water, diversity of jobs), acceptable risk levels, and suitable harvest amounts and patterns. Timber companies can then design logging plans or bid on open log markets and focus on manufacturing, where their expertise lies, rather than on forest management.
Regional log markets provide timber to small manufacturers.
Local residents find jobs in forest trusts or community-based authorities and manufacturing.
The traditional business model of forest companies no longer applies; new models have little to do with sustainability and much to do with highly mobile transboundary capital, lowest cost investment and little place-based accountability.
Changing tenure provides opportunities for ENGOs such as The Nature Conservancy to manage and/or purchase and protect land.
Community forests and First Nations’ woodland licences in BC have a variety of management approaches. Some are focused on providing economic benefit to communities; many aim to achieve sustainable management certification.
The Algonquin Forest Authority provides a business structure model that manages landscape as a public tenure ownership.
Quebec forestry has shifted from industrial to government control of forest management. This has had unexpected consequences, with government foresters less inclined to follow outside recommendations; perhaps a mixed model might be best.
The First Nations owned Menominee Forest in Wisconsin has been sustainably harvested for more than 150 years, prioritising removal of low-quality trees and keeping vigorous trees, guided by ecology but still highly profitable.
Wildwood Ecoforestry Institute Society on Vancouver Island has continued Merv Wilkinson’s legacy of ecologically and economically sustainable forestry.
1. International Panel on Climate Change. https://www.ipcc.ch/. Any recent reports.
2. Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. https://www.ipbes.net/
3. For example, IBPES Pandemics Report: Escaping the Era of Pandemics. https://www.ipbes.net/pandemics. UNEP 2021. delves into humanity’s triad of emergencies: climate, biodiversity and pollution. It synthesises global environmental assessments produced by the Intergovernmental Panel on Climate Change, Intergovernmental Science-Policy Platform for Biodiversity and Ecosystems Services, and the United Nations Environment Program.
4. For example, Moore, P., Noonan, D., & Woodward, E. 2020. Juliana v. United States and the global youth-led legal campaign for a safe climate. In Standing up for a Sustainable World. Edward Elgar Publishing.
6. Primary forest is forest of any age that has not been disturbed by industrial activities. Not all primary forest is old, but all old growth is primary forest. Old growth forest reflects a landscape’s natural disturbance regime. In wet regions, where disturbance is rare, old growth forest replaces itself over time as small gaps open and fill, providing a complex, dynamically stable environment for centuries. Where disturbances are more frequent, old growth forest is more uniform, with veteran trees representing legacies of past disturbance.
7. Smith RB 2020. Enhancing Canada’s Climate Change Ambitions with Natural Climate Solutions. Vedalia Biological Inc. http://doi.org/10.13140/RG.2.2.18243.02088/ Protection of the most carbon-dense ecosystems, under imminent threat, would remove 10Mt C02per year from the atmosphere immediately to over 175 Mt CO2 per year by 2030. Emissions of 586 Mt CO2 would be avoided by maintaining stores under imminent threat. This would increase to 1.8 to 11 billion tonnes of CO2 by 2030 and to 35 – 186 Gt of CO2 e by 2050. In BC, remaining high-productivity old growth forests store 200 – 470 Mt of carbon (lower estimate excludes soil carbon). Remaining area of these forests from Price et al. 2020. BC’s Old Growth Forests: A Last Stand for Biodiversity. Luyssaert, S., Schulze, E. D., Börner, A., Knohl, A., Hessenmöller, D., Law, B. E., ... & Grace, J. 2008. Old-growth forests as global carbon sinks. Nature, 455(7210), 213-215.Law, B. E., Hudiburg, T. W., Berner, L. T., Kent, J. J., Buotte, P. C., & Harmon, M. E. 2018. Land use strategies to mitigate climate change in carbon dense temperate forests. Proceedings of the National Academy of Sciences, 115(14), 3663-3668. “Here, we demonstrate this approach in a high biomass region, and found that reforestation, afforestation, lengthened harvest cycles on private lands, and restricting harvest on public lands increased net ecosystem carbon balance by 56% by 2100, with the latter two actions contributing the most. Forest sector emissions tracked with our life cycle assessment model decreased by 17%, partially meeting emissions reduction goals. Harvest residue bioenergy use did not reduce short-term emissions. Cobenefits include increased water availability and biodiversity of forest species. Our improved analysis framework can be used in other temperate regions.”
8. Pojar 2019. Forestry and carbon in BC: 7 forest carbon myths, misconceptions, or oversimplifications Smith 2020. Law et al. 2018.
9. Pojar J 2019. Forestry and carbon in BC: 7 forest carbon myths, misconceptions, or oversimplifications; Smith 2020.
10. Frey SJ, Hadley AS, Johnson SL, Schulze M, Jones JA, Betts MG. (2016). Spatial models reveal the microclimatic buffering capacity of old-growth forests. Science Advances 2(4): e1501392. Bradley, C.M., Hanson, C.T. and DellaSala, D.A., 2016. Does increased forest protection correspond to higher fire severity in frequent‐fire forests of the western United States? Ecosphere, 7(10), p.e01492. Zald, H. S., & Dunn, C. J. 2018. Severe fire weather and intensive forest management increase fire severity in a multi‐ownership landscape. Ecological applications, 28(4), 1068-1080. Watson, J. E., Evans, T., Venter, O., Williams, B., Tulloch, A., Stewart, C., ... & Lindenmayer, D.2018). The exceptional value of intact forest ecosystems. Nature ecology & evolution, 2(4), 599-610.
11. Watson, J. E., Evans, T., Venter, O., Williams, B., Tulloch, A., Stewart, C., ... & Lindenmayer, D. 2018. The exceptional value of intact forest ecosystems. Nature ecology & evolution, 2(4), 599-610.
2021-04 Informing Land Use Planning with Science.pdf