Traits influence responses to land-use and climate change in terrestrial vertebrates

Human activities have profoundly impacted global biodiversity. Currently, anthropogenic land-use and climate change figure among the major threats to the world’s fauna. However, not all species respond similarly to these pressures. Interspecific variability in responses to human threats is notably underpinned by the fact that different species possess different ecological characteristics, some of them allowing species to cope with environmental changes, while others confer a disadvantage to species in modified environments. Understanding what renders species sensitive to anthropogenic pressures is vital to inform and prioritise conservation efforts. Yet, in terrestrial vertebrates, a group for which ecological data are the most abundant, it remains unclear which traits are associated with higher sensitivity to human pressures. The aims of my thesis are to investigate whether and which traits are associated with land-use responses and climate-change sensitivity in terrestrial vertebrates, and to highlight some of the consequences for ecosystem functioning. I first assess the global availability of ecological trait data for terrestrial vertebrates, identifying understudied groups and regions (e.g., Central-African reptiles). I then show that, at global scales, disturbed land uses negatively impact the functional diversity of vertebrate assemblages. Further, I find that in all classes, higher sensitivity to land-use and climate change is associated with narrower ranges, smaller habitat breadth and inability to use human-modified habitats. Both land-use responses and climate-change sensitivity are unevenly distributed among dietary groups, highlighting potential food-web disruptions in assemblages under pressure. Finally, I show that land-use responses are influenced by species’ energetic requirements, so that energetic fluxes within vertebrate assemblages are likely modified under human-driven land-use change. Although the large-scale consequences of biodiversity changes for ecosystem functioning remain to be fully understood, my thesis highlights a compositional reshaping of vertebrate assemblages under human pressure and furthers our understanding of anthropogenic impacts on biodiversity

Impacts of the global food system on terrestrial biodiversity from land use and climate change

The global food system is a key driver of land-use and climate change which in turn drive biodiversity change. Developing sustainable food systems is therefore critical to reversing biodiversity loss. We use the multi-regional input-output model EXIOBASE to estimate the biodiversity impacts embedded within the global food system in 2011. Using models that capture regional variation in the sensitivity of biodiversity both to land use and climate change, we calculate the land-driven and greenhouse gas-driven footprints of food using two metrics of biodiversity: local species richness and rarity-weighted species richness. We show that the footprint of land area underestimates biodiversity impact in more species-rich regions and that our metric of rarity-weighted richness places a greater emphasis on biodiversity costs in Central and South America. We find that methane emissions are responsible for 70% of the overall greenhouse gas-driven biodiversity footprint and that, in several regions, emissions from a single year's food production are associated with global biodiversity loss equivalent to 2% or more of that region's total land-driven biodiversity loss. The measures we present are relatively simple to calculate and could be incorporated into decision-making and environmental impact assessments by governments and businesses

Six-Month Mortality among HIV-Infected Adults Presenting for Antiretroviral Therapy with Unexplained Weight Loss, Chronic Fever or Chronic Diarrhea in Malawi.

In sub-Saharan Africa, early mortality is high following initiation of antiretroviral therapy (ART). We investigated 6-month outcomes and factors associated with mortality in HIV-infected adults being assessed for ART initiation and presenting with weight loss, chronic fever or diarrhea, and with negative TB sputum microscopy

Species-level correlates of land-use responses and climate-change sensitivity in terrestrial vertebrates

Land-use and climate change are two major pressures on terrestrial biodiversity. Species' extinction risk and responses to human pressures have been shown to relate to ecological traits and other characteristics in some clades. However, we lack large-scale comparative assessments of the associations between traits and responses to multiple human pressures, across multiple clades. Here, we investigated whether a set of ecological characteristics that are commonly measured across terrestrial vertebrates (ecological traits and geographical range area) are associated with: (1) species' responses to different land-use types; and (2) species' likely sensitivity to climate change (based on properties of their realized climatic niche). Our aim was to test whether generalisable patterns in response to these pressures arise across both pressures and across vertebrate clades, which could help to assess the global signature of human pressures on vertebrate biodiversity, and to guide conservation efforts. Among the characteristics we considered, only three were consistently associated with strong land-use responses and high climate-change sensitivity across terrestrial vertebrate classes: narrow geographical range area, narrow habitat breadth and specialisation on natural habitats. The associations of other traits with species' land-use responses and with climate-change sensitivity often depended on class and land-use type, highlighting an important degree of context dependency. In all classes, invertebrate eaters and fruit/nectar eaters tended to be negatively affected in disturbed land uses, while invertebrate- and plant/seed-eating birds were estimated to be more sensitive to climate change, raising concerns about the continuation of ecological processes sustained by these species under global changes. Our work highlights a consistently higher sensitivity for narrowly distributed species and habitat specialists under land-use and climate change, which provides support for capturing such characteristics in large-scale vulnerability assessments

Effects of rarity form on species' responses to land use

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