Extinction debt in local habitats: quantifying the roles of random drift, immigration and emigration

Abstract

We developed a time-dependent stochastic neutral model for predicting diverse temporal trajectories of biodiversity change in response to ecological disturbance (i.e. habitat destruction) and dispersal dynamic (i.e. emigration and immigration). The model is general and predicts how transition behaviours of extinction may accumulate according to a different combination of random drift, immigration rate, emigration rate and the degree of habitat destruction. We show that immigration, emigration, the areal size of the destroyed habitat and initial species abundance distribution (SAD) can impact the total biodiversity loss in an intact local area. Among these, the SAD plays the most deterministic role, as it directly determines the initial species richness in the local target area. By contrast, immigration was found to slow down total biodiversity loss and can drive the emergence of species credits (i.e. a gain of species) over time. However, the emigration process would increase the extinction risk of species and accelerate biodiversity loss. Finally but notably, we found that a shift in the emigration rate after a habitat destruction event may be a new mechanism to generate species credits.

Extinction of biotic interactions due to habitat loss could accelerate the current biodiversity crisis

“…Alternatively, large initial habitat losses may produce fewer than expected extinctions and so fewer than predicted orphaned species, at least in the short term. Areas subjected to habitat loss accumulate extinction debt (Tilman et al, 1994) because extinctions take generations to be realized (Wearn et al, 2012), and can be mitigated by immigration or recolonization from nearby habitat patches (Hanski & Ovaskainen, 2002; Wu et al, 2020). We assumed that primary extinctions and orphaned species occurred at each area loss step with habitat destruction, but in real situations, extinctions, and associated orphaned species, could take decades to occur.…”

Clinging to survival: Critically Endangered Chapman's pygmy chameleon Rhampholeon chapmanorum persists in shrinking forest patches

“…Erosion of genetic diversity at detectable levels has a long time lag that is influenced by the effective population size, the number of generations and the degree of habitat loss and fragmentation (e.g. Tilman et al, 1994; Krauss et al, 2010; Hoban et al, 2014; Wu et al, 2020). Conversely, genetic structure responds more rapidly to habitat fragmentation (Keyghobadi et al, 2005; Pflüger et al, 2019) because gene flow is impeded by isolation of local patches (Balkenhol et al, 2013).…”

Myoglobin as a conservation‐relevant predictor of short‐distance flight capacity in Neotropical forest birds

“…Habitat fragmentation produces landscapes characterized by spatially isolated remnants, many of which lose species through time (Dirzo & Raven, 2003). An important explanation for such species loss is disruption of dispersal between patches, distorting immigration–emigration dynamics, even among vagile species like birds (Wu et al, 2020). Some tropical forest bird species, in particular those of the forest understory, appear to be reluctant or unable to fly across habitat discontinuities, leading to inevitable species loss in fragments as recolonization is reduced or eliminated (Gillies et al, 2011; Laurance & Gomez, 2005; Robinson & Sherry, 2012; Van Houtan et al, 2007; Willis, 1974).…”