How do habitat amount and habitat fragmentation drive time-delayed responses of biodiversity to land-use change?

Abstract

Land-use change is a root cause of the extinction crisis, but links between habitat change and biodiversity loss are not fully understood. While there is evidence that habitat loss is an important extinction driver, the relevance of habitat fragmentation remains debated. Moreover, while time delays of biodiversity responses to habitat transformation are well-documented, time-delayed effects have been ignored in the habitat loss versus fragmentation debate. Here, using a hierarchical Bayesian multi-species occupancy framework, we systematically tested for time-delayed responses of bird and mammal communities to habitat loss and to habitat fragmentation. We focused on the Argentine Chaco, where deforestation has been widespread recently. We used an extensive field dataset on birds and mammals, along with a time series of annual woodland maps from 1985 to 2016 covering recent and historical habitat transformations. Contemporary habitat amount explained bird and mammal occupancy better than past habitat amount. However, occupancy was affected more by the past rather than recent fragmentation, indicating a time-delayed response to fragmentation. Considering past landscape patterns is therefore crucial for understanding current biodiversity patterns. Not accounting for land-use history ignores the possibility of extinction debt and can thus obscure impacts of fragmentation, potentially explaining contrasting findings of habitat loss versus fragmentation studies.

Why Do Agroforestry Systems Enhance Biodiversity? Evidence From Habitat Amount Hypothesis Predictions

“…Additionally, even if the HAH predictions seem to integrate the metapopulation dynamics theory (Semper-Pascual et al, 2021), by holistically considering that extinction probability decreases as the size of patches of habitat increase (assuming that expected population size is positively correlated with overall habitat area), the distributions of organisms do not always reflect the distribution of suitable habitats (Merckx et al, 2019). Population dynamics were not explicitly considered in our simple model, nor changes in quality of the micro-habitats present (Gardiner et al, 2018).…”

Land Use and Ecological Change: A 12,000-Year History

“…These differential and lagged responses are characterized as extinction debt when extinctions lag behind land use changes, such as when long-lived tree species lose their pollinators or seed dispersers, and as extinction filtering when the most vulnerable species are lost early, leaving communities of species better adapted to dynamic cultural landscapes and therefore less vulnerable to future changes (179). As a result of extinction debt and filtering, land use changes of the past, and their evolutionary consequences, can play a critical role in shaping current and future rates of extinction (127,129,130). low-tillage practices are introduced (88,118).…”

“…Deforestation and reforestation can both increase and decrease streamflow (126). The evolutionary consequences of early land use, including burning, habitat fragmentation, population declines in prey and other species, and the adaptations of remaining species to cultural landscapes, can produce legacy effects that can lower and/or obscure future rates of extinction through extinction filtering and extinction debt, respectively, while also shaping diverse and resilient novel communities and ecosystems (19,27,39,98,99,(127)(128)(129)(130); see also the sidebar titled Extinction Filtering and Extinction Debt). Given these complex, divergent, and often opposing ecological consequences, detailed reconstructions of long-term land use histories are essential to better understand the legacies of past land use and to enable more effective environmental governance in the future.…”

Spatially explicit models for decision‐making in animal conservation and restoration

“…Likewise, rewilding apex predators may be unsuccessful in a policy context that does not regulate poaching (Bleyhl et al 2021), and riparian habitat restoration may be inefficient when pollution sources are not eliminated first. Quantifying whether stressors affect biodiversity additively or synergistically requires improved environmental data, including past time series when studying legacy effects (Semper-Pascual et al 2021) and future scenarios to inform decision-making. A key challenge is thus to provide integrated scenarios of climate, land use, and other anthropogenic pressures at finer spatial resolution in order to inform regional conservation and restoration efforts.…”

“…First, species and ecosystems may not be at equilibrium with their environment but could exhibit legacy effects. In systems with a time‐delayed response, for example, extinction debts due to past habitat loss (Semper‐Pascual et al 2021), even immediate conservation actions may not be able to halt biodiversity loss in its entirety. Second, biodiversity and ecosystems respond dynamically to global change, and conservation actions need to anticipate these dynamics (Araújo et al 2011, Oliver et al 2016).…”