Functional implications of land use and climate change on bird assemblages worldwide
File(s)
Author(s)
Walkden, Patrick
Type
Thesis
Abstract
Human well-being and sustainable development depend on ecosystems delivering contributions to people now and in the future. However, pervasive anthropogenic pressures on biodiversity threaten ecosystems’ potential to perform essential processes and functions. Understanding functional implications of human-driven biodiversity change worldwide, and how they might be mitigated, is therefore an urgent research priority. Functional diversity – the diversity and distribution of functional traits – can better predict ecosystems’ functional resilience to environmental perturbations than species richness. Trait-based approaches may support achieving global biodiversity targets to reverse biodiversity loss and enhance ecosystem functioning, such as the Kunming-Montreal Biodiversity Framework (KMGBF). In this thesis, I collate, integrate and curate large global datasets of bird assemblage composition, population trends and functional traits to assess the implications of land-use and climate change for bird assemblages. I first demonstrate the potential of functional trait approaches in measuring ecosystem integrity, a key component of KMGBF’s Goals A and B. I show that human modification of natural habitats erodes ecosystem integrity by driving contraction, shifts and internal erosion of avian trait space, with impacts varying across groups and associated processes. Second, I address the lack of a biodiversity indicator based on functional trait data by proposing and prototyping the Functional Intactness Index (FII). FII is a model-based indicator that estimates the degree to which an ecological assemblage has retained functional diversity expected in the absence of human impacts. I make global projections of FII in 2000 and 2020 that may identify regions of conservation priority. Finally, I show species’ functional traits influence their population responses to anthropogenic pressures in North America. Mechanisms underpinning population change arise from interactions between species’ traits and exposure to environmental pressures, highlighting the need for a holistic approach to conservation decision-making considering this context-dependency.
Version
Open Access
Date Issued
2024-06-27
Date Awarded
01/01/2025
License URL
Advisor
Purvis, Andy
Tobias, Joseph
Sponsor
Natural Environment Research Council (Great Britain)
Grant Number
NE/S007415/1
Publisher Department
Life Sciences
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)