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Nov
19
2009
Decline of large animals drove changes in plants and fires
With the help of a dung fungus, scientists have figured out that the disappearance of mammoths, mastodons, and other large animals likely caused dramatic changes in North American plant communities and fire frequency – not the other way around.
Between roughly 10,000 and 20,000 years ago, North America went on an ecological rollercoaster ride: many large mammal species died out, new combinations of plants flourished, fires increased in frequency and intensity, and the climate swung back and forth between cold and hot. But which event caused which?
Researchers decided to look for answers in a fungus called Sporormiella, which leaves spores on mammal and bird dung. The more fungal spores, they reasoned, the more large mammals there must have been. By analyzing spores, pollen, and charcoal from a lake in Indiana, the team could reconstruct a history of the period’s ecological changes.
Spore numbers dropped from 14,800 to 13,700 years ago, suggesting that large mammals also declined during that time. New plant communities began to form 13,700 years ago, and charcoal – indicative of fires – began spiking 14,100 years ago, followed by an increase at 10,700 years ago, the team reports in Science.
Therefore, the idea that climate-driven changes in plant communities wiped out megafauna doesn’t appear to hold water, the researchers say. Instead, they write, the decline of large herbivores probably allowed certain trees to thrive and caused fuel to accumulate, leading to more fires.
The data do not reveal whether climate changes or human activities killed off the animals. More work on the causes and effects of these extinctions could lead to a better understanding of how changes in today’s plant-eating animal populations will affect their ecosystems, the team writes. – Roberta Kwok
Source: Gill, J., Williams, J., Jackson, S., Lininger, K., & Robinson, G. (2009). Pleistocene Megafaunal Collapse, Novel Plant Communities, and Enhanced Fire Regimes in North America Science DOI: 10.1126/science.1179504
Image © kim258, iStockPhoto.com
Filed Under Biodiversity, Climate change |
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