Climate change, land use and other human-driven factors could pit savannas and forests against each other by altering the elements found by Princeton University researchers to stabilize the two. Without this harmony, the habitats, or biomes, could increasingly encroach on one other to the detriment of the people and animals that rely on them.
The Princeton researchers reported this month in the journal Science that savanna wildfires, combined with climate conditions, maintain the distinct border between savannas and forests in many tropical and subtropical areas. Savanna fires keep tree cover low and prevent forests from encroaching on the grassland. When tree cover is high, as in a forest, fires cannot spread as easily, halting the savanna's advance into the forest.
But the Princeton team's findings suggest that savanna wildfires could be heavily influenced by factors such as climate change, road construction and fire-prevention measures. Less rainfall can result in an uptick in fires that can transform a forest into a savanna, just as breaking up the landscape through road construction and fire control disrupt natural blazes and allow a forest to sprout where there once was a savanna.
The researchers suggest that because of these factors, large stretches of South American and African forest and savanna could degenerate into chaotic mutual encroachment. The changeover from one biome to the other -- which can happen within several decades -- can be extremely difficult to reverse once it has happened, explained lead author Carla Staver, a doctoral student in the laboratory of co-author Simon Levin, the Moffett Professor of Biology in Princeton's Department of Ecology and Environmental Biology. She and Levin worked with co-author Sally Archibald, a senior research scientist at the Council for Scientific and Industrial Research in South Africa.
Plants and animals that thrive in a forest or savanna often cannot transiti
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