Global interannual variability in terrestrial ecosystems : patterns, sources, and impacts on biodiversity and human security
(2008)
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- Abstract
- A better understanding of global earth system processes requires increasingly detailed information on global ecosystem changes. This thesis focuses on monitoring the spatial and temporal dynamics in ecosystems using coarse-resolution remote sensing data at regional and global scales. It further investigates the impact of climate change, land use, and other natural and anthropogenic disturbances, on interannual variability in land surface attributes in different ecosystems. Using this methodology, the potential influences of vegetation variability on ecological systems and human societies directly dependent on local ecosystem goods and services are also evaluated. For the first time, global-scale maps representing interannual variability in land surface attributes, as well as the different processes characterizing them, are produced. The analyses of these global maps reveales the high spatial and temporal heterogeneity in ecosystem dynamics. Over 10 million km2 of the study area experience high interannual variability in land surface attributes over the 6 years, affecting certain ecozones more than others. These observed fluctuations in vegetation are largely driven by rainfall variability and associated with mean annual rainfall, agriculture, fire regimes, and population density. With the enhanced monitoring of interannual variability of vegetation cover and understanding of its main sources, this thesis further assesses the influence of such "fast" land changes on ecological systems. The results presented here, highlight the importance of ecosystem variability as a driver of species richness. When controlling for vegetation production, species richness is greatest in more stable ecosystems. The study also provides insight on how vegetation variability affect species with different migratory strategies. Finally, it is shown here that, in the Horn of Africa, the availability and stability of vegetation productivity is associated with human security. Ephemeral land changes are related to the onset of violence indirectly, through an increase in undernourished population. The study also reveals the relationship, in low-income countries, between the local economic activity and accessibility, and malnutrition and insecurity. Climate change, with its long- and short-term effects on ecosystem production, has the potential to destabilize entire regions.
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Rowhani Ardekani, P. (2008). Global interannual variability in terrestrial ecosystems : patterns, sources, and impacts on biodiversity and human security. https://hdl.handle.net/2078.5/98060