The Andes Mountains in South America are home to a rich diversity of plants and animals, but they also bear the scars of human and natural influences.
A new study reveals how ancient humans used fire to alter the landscape, creating a new ecosystem that persists to this day.
The study also shows how climate change affects the ability of the Andean forests to store carbon, a vital service for mitigating global warming.
Fire as a tool and a threat
The study, published in Nature Communications, combines archaeological and paleoenvironmental data from 119 forest-monitoring plots in Colombia, Ecuador, Peru, Bolivia and Argentina.
The researchers found that humans moved into the Andes about 15,000 years ago and introduced regular fire to the landscape. This prevented the regrowth of the region's forests, creating a sprawling bushland that exists today.
"This is the earliest evidence I have seen of humans fundamentally transforming their ecosystem with fire," said Alvaro Duque, the lead author of the study and a professor at the Universidad Nacional de Colombia Sede Medellín.
"It suggests that by the Late Pleistocene, humans were learning to use fire in truly novel ways. In this case, their burning caused replacement of the region's forests with the open woodlands you see today."
The researchers also found that the human-induced fires increased the frequency and intensity of natural fires, which further shaped the vegetation and soil.
The fires also affected the biodiversity of the region, favoring fire-adapted species and reducing the habitat for forest-dependent species.
However, the study also warns that the current rate and extent of human-caused fires in the Andes are unsustainable and pose a serious threat to the ecosystem and its services.
The researchers urged for more effective fire management and conservation policies to protect the Andean forests and their biodiversity.
Also Read: Beneath the Andes Mountains: Earth's Crust 'Dripping' Into the Planet's Interior
Carbon storage and climate change
Another important finding of the study is that the Andean forests are helping to protect the planet by acting as a carbon sink, absorbing more carbon dioxide than they emit.
The researchers estimated that the aboveground biomass of the Andean forests increased by 0.6% per year between 2005 and 2015, storing about 0.23 gigatons of carbon.
"Carbon storage is one of the most important ecosystem services that helps to mitigate the effects of rising carbon dioxide levels under climate change and temperature warming," said Jonathan Myers, a co-author of the study and an associate professor of biology at Washington University in St. Louis.
"This study provides insights into how species on the move, under climate change, might be impacting these broader ecosystem services important to humanity," he said
The study also found that the carbon storage potential of the Andean forests varies with elevation and climate.
The forests at lower elevations, which are warmer and wetter, store more carbon than those at higher elevations, which are cooler and drier.
However, the researchers also found that the forests at higher elevations are more resilient to climate change, as they have experienced more climatic fluctuations in the past.
The researchers suggested that the Andean forests could adapt to future climate change by shifting their ranges upslope, following the optimal conditions for growth and carbon storage.
However, this would also depend on the availability of suitable habitat and the ability of the species to disperse and colonize new areas.
The researchers concluded that the Andean forests are a valuable natural resource that deserves more attention and protection.
They called for more research and monitoring to understand the dynamics and drivers of the Andean forests and their carbon storage capacity, as well as the impacts of human activities and climate change on their biodiversity and ecosystem services.
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