Research led by physicists and geographers from the University of Cambridge has uncovered some large-scale changes in vegetation in the South American Andes that could have dramatic effects on the region’s environment and ecosystems.

A research team from the Cavendish Laboratory in Cambridge analyzed satellite data from the past 20 years to examine how vegetation has changed along Peru’s Pacific coast and northern Chile. This area is known for its unique and delicate arid and semi-arid environments.

The analysis showed that some areas experienced positive plant growth known as greening, while others experienced negative trends known as browning. Not surprisingly, changes in vegetation are affected by things like agriculture and urban development or changes in land use practices.

But even more interesting is a published study. Remote sensing revealed the discovery of a large area of ​​the West Slope of the Andes that has been significantly greened over the past 20 years. Stretching from northern Peru to northern Chile, this region covers a length of about 2,000 km and has seen significant vegetation growth over time. This greening trend varies with height, with different types of plants at different heights.

A research team of mathematicians, geographers, biologists and geoscientists used satellite imagery from 2000 to 2020 to observe changes in vegetation in the area. They identified 450 data points and developed a mathematical model to eliminate artificial fluctuations (such as cloudy days) and seasonality, and used statistical analysis to ensure they were only analyzing areas with a significant trend.

“It took three years to figure out the methodology and statistical model,” said Hugo Lepage, a mathematician at the Cavendish Laboratory and lead author of the study. “We had to make it bulletproof to make sure something was on a really large scale and it wasn’t a coincidence.”

To confirm what they saw in the data, the researchers made multiple trips to make observations on the ground to confirm their numerical claims.

“We started from a very local area to study the impact of mining on local vegetation,” said Eustace Barnes, a geographer in the Cavendish Laboratory Environmental Physics Group, who led the research. “To our surprise, the data shows that this area has become greener, not darker. So we zoomed out and noticed that other areas were also greening on a large scale. We noticed a similar trend when we went to check the ground.”

In addition to the empirical observation of the green band, the researchers marveled at its surprising properties.

“First, when we look south, the band rises, going from 170-780m in northern Peru to 2600-4300m in southern Peru,” Barnes said. “This is implausible as we expect the surface temperature to decrease both as we move south and as we rise.”

Even more surprising is that this large area of ​​greening does not correspond to the climatic zones generated by the Köppen-Geiger classification, a widely used empirical climate classification system based on vegetation, but is well matched to the greening and browning trends in coastal deserts and the high Andes.

“Actually, in northern Peru, the green belt is mostly located in the climate zone that corresponds to the hot and arid desert,” Lepage said. Said. “As we sweep the southbound band, it rises towards the hot and dry steppe and finally crosses the cold and dry steppe. It’s not what we expected given the climate in these regions.”

The results of this study have far-reaching implications for environmental management and policy making in the region. While the exact cause or effects of this greening are unknown, any significant change in vegetation (an index increase of 30-60%) is bound to have an impact on ecosystems and the environment.

“The Pacific Slope supplies water to two-thirds of the country and is where most of Peru’s food comes from,” said Barnes. “This rapid change in vegetation as well as water levels and ecosystems will inevitably affect water management and agricultural planning.”

The researchers believe their findings will greatly improve the scientific community’s understanding of the complex interactions between climate change and sensitive ecosystems in arid and semi-arid environments.

“It’s a warning sign, like a canary in the mine. There’s nothing we can do to stop change on such a large scale. But knowing this will help you plan better for the future,” Lepage concluded. Source