Lera Miles
Species’ ranges are configured according to their tolerance of environmental conditions, especially climate, and their history of dispersal since speciation. Previous studies of the potential impact of climate change on biodiversity have been biased towards species of high latitudes. This situation results from a lack of detailed knowledge about the distribution of tropical biodiversity, and from the smaller degree of warming expected at low latitudes. However, various General Circulation Models (GCMs) simulate regional drying and increasing seasonality for parts of the tropics, including Amazonia. This may have a greater impact on tropical forest flora than temperature change alone. The Amazon region holds a high proportion of global biodiversity, yet conservation plans rarely consider possible climate change impacts.
This thesis presents a methodology for projecting a set of Amazonian plant species’ ranges from limited data, and estimating their response to climate change scenarios. Species are classified into plant functional types (PFTs), which share traits such as growth form and reproductive strategy. Species' current distributions are modelled over a coarse scale (a 1º latitude-longitude grid), using a suitability index based on bioclimate variables. Distributions are additionally limited by species’ absolute tolerances to extreme values, and by dispersal barriers. A sizestructured population is simulated for each cell, to enable modelling of lags in response to climate change.
In the standard impact scenario (SIS), future population processes are simulated over 100 years, with changes in the variables governing cell suitability being applied annually according to anomalies from a selected GCM. The run is repeated for each species using anomalies of half that magnitude, as a reduced-impact scenario (RIS).
The range of potential outcomes for each species and PFT is evaluated. Widespread impacts are seen under both scenarios. An alternative impact scenario (AIS) is devised to examine the effects of allowing some "c-species" to thrive under heightened AET. The most vulnerable taxonomic groups, PFTs and geographical regions are identified as targets for monitoring and conservation action. In particular, there is a dramatic loss of species' viability in much of northeastern Amazonia at 2095 under all scenarios. The far western part of Amazonia is identified as important for persistence of the greatest number of species. Areas falling between the major rivers of the region have very limited distribution data, so are highlighted for future biodiversity survey work.
The Impact of Global Climate Change on Tropical Forest Biodiversity in Amazonia on White Rose Etheses Online
Title page, Acknowledgements, Abstract, Tables of contents and figures, and introductory chapter including Aims and Objectives and Key Definitions
Background information on Amazonian climate, vegetation and human impacts, together with a discussion of the origins and patterns of Amazonian biodiversity patterns and plant functional requirements that affect their distribution.
A review of global climate models and scenarios and their relevance to the Amazon region. The Hadley Centre HADCM2 model is chosen for use in this simulation.
A review of the functional and distributional responses of plants to climate, and existing methods for modelling current and changing distributions.
A methodology for modelling tropical species' response to climatic change is developed and applied to the Amazon region. Criteria are defined and applied to select a set of species to represent Amazonian genetic and functional biodiversity.
Outcomes of the regional climate simulation, the variables most affected by climate change, and maps of present and changing distributions.
Identification of common patterns of distributional change, change in population density, and plant traits associated with different outcomes.
Discussion of model outcomes, validation of aspects of the method, and discussion of the implications of the study including a comparison with outcomes of vegetation-climate models. Recommendations for conservation action and future research.
Glossary, Appendices and References.