Zhang Integrative Ecology Lab | ZIEL

Rewilding is emerging as a promising restoration strategy to tackle the challenges posed by global change and maintain natural ecosystems and their biodiversity. However, rewilding has also been criticized for the absence of a consistent definition and insufficient knowledge about its possible outcomes. Here, we explored the effects of rewilding on filling functional gaps created by the extirpation of native species. We contrasted rewilding with three other mechanisms for change in community composition?species extirpation, species introduction, and unassisted colonization?in terms of their impacts on changes in avian and mammalian diversity in the UK. We found that (i) while rewilding increases functional diversity most on average, introduced/naturalized birds contribute more functional uniqueness to native functional space than other groups of birds; and (ii) changes in functional diversity associated with ?rewilded? organisms were species-dependent and idiosyncratic. Our results suggest that although rewilding can expand or infill native functional trait space to some extent, such effects require careful assessment.

Aim:Geographic structure is a fundamental organising principle in ecological and Earth sciences, and our planet is conceptually divided into distinct geographic clusters (e.g. ecoregions and biomes) demarcating unique diversity patterns. Given recent advances in technology and data availability, however, we ask whether geographically clustering diversity time-series should be the default framework to identify meaningful patterns of diversity change.
Location:North America.
Taxon: Aves.
Methods: We first propose a framework that recognises patterns of diversity change based on similarities in the behaviour of diversity time-series, independent of their specific or relative spatial locations. Specifically, we applied an artificial neural network approach, the self-organising map (SOM), to group time-series of over 0.9 million observations from the North American Breeding Birds Survey (BBS) data from 1973 to 2016. We then test whether time-series identified as having similar behaviour are geographically structured.
Results: We find little evidence of strong geographic structure in patterns of diversity change for North American breeding birds. The majority of the recognised diversity time-series patterns tend to be indistinguishable from being independently distributed in space.
Main Conclusions: Our results suggest that geographic proximity may not correspond to shared temporal trends in diversity; assuming that geographic clustering is the basis for analysis may bias diversity trend estimation. We suggest that approaches that consider variability independently of geographic structure can serve as a useful addition to existing organising rules of biodiversity time-series.

Halting and reversing biodiversity loss is a grand challenge in the Anthropocene, which suggests an urgent need to effectively protect key areas that support species sustainability. However, large knowledge gaps exist in determining those key areas for migratory species and the extent to which they are protected, albeit with the essential and indispensable functions that migratory species perform in biodiversity conservation. Here, we used over 390 million community-contributed bird observations to derive order-specific, spatially explicit estimates of annual migration networks for 26 bird orders across the world. We found that 35% of the overall 343 important sites that strongly connect the migration network across the annual cycle of global migratory birds are uncovered by protected areas. This leads to nearly 87% of 1,862 migratory bird species being at risk. Migratory species benefit more from considering various levels of site importance to safeguard network integrity, with conservation efforts across countries.

Recent studies have drawn contrasting conclusions about the extent to which local-scale measures of biodiversity are declining, and whether such patterns conflict with the global-scale declines that have attracted much attention. A key source of high quality data for such analyses comes from longitudinal biodiversity studies which sample a given taxon repeatedly over time at a specific location. There has been relatively little consideration of how habitat change might lead to biases in the sampling and continuity of biodiversity time-series data, and the consequent potential for bias in the biodiversity trends that result. Here, based on analysis of standardised routes from the North American Breeding Bird Survey (3014 routes sampled over 18 years), we demonstrate that major local habitat change is associated with an increase in the rate of survey cessations. We further show that routes that were continued despite major habitat changes show reduced diversity. By simulating potential rates of loss, we show that the underlying real trends in taxonomic, functional and phylogenetic diversity can even reverse in sign if more than a quarter of diversity is lost from routes that ceased, and are thus no longer included in surveys. Our analyses imply that biodiversity loss can be underestimated by biases introduced if continued sampling in longitudinal studies is influenced by local change. We argue that researchers and conservation practitioners should be aware of the potential for bias in such data and seek to use more robust methods to evaluate biodiversity trends and make conservation decisions.