Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Monsoons, wildfires, and savannas : drivers of climate and ecosystem change in Northwest Africa

Auteur : O’Mara, Nicholas Alexander

Université de soutenance : Columbia University

Grade : Doctor of Philosophy (PhD) 2022

Résumé partiel
Open grassy environments in Africa have been key landscapes for the development and evolution of humans and our hominid ancestors for millions of years. These environments have not been static, however, as global climate changes have strongly shaped their nature and location over time. In the modern, at least 80 million people living in Sub-Saharan Africa rely on agriculture and pastoralism within the grasslands and savannas of the Sahel region alone for food security. Devastating droughts and associated famine in the region over the past several decades have highlighted this region’s potential vulnerability to future climate change. Wildfires play a unique and critical role in maintaining Africa’s grasslands and savannas, especially in the Sahel region. Emissions from these fires have additional ramifications for the Earth’s radiative balance and global cycles of carbon and nutrients. As populations in Africa rise over the coming century from 1.3 billion to 4 billion people by 2100, increasing demand for food, rising temperatures, and highly uncertain changes in rainfall and wildfire patterns are poised to put the people and ecosystems of this region in jeopardy.

In the face of potentially novel environmental conditions resulting from anthropogenic climate change, this research aims to better understand the long-term interconnections of climate, ecology, and human presence in Northwest Africa and how these linkages may vary under broad shifts in climate. Accurate projections of future climate and ecosystem change not only require the mechanistic understanding of climate forcings and climate-ecosystem interactions that can be gleaned from modern relationships, but also information about how these interactions may vary as a function of changes in the background climate state itself (on centennial to million year timescales). Highly spatially-resolved satellite measurements relevant for asking such questions only extend back a few decades and thus only provide a limited perspective on whether or not modern climate-ecosystem interactions are stationary through time.

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