Habitat thresholds as guidance for forest management and conservation

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.

Precaution

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

Probability approach

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).

Conclusions

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. 

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 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. 

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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). 

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56 Steffen et al. (2015). (see Note 54). 

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59 Lade et al. (2021). (See Note 58). 

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