We tend to think the main threats of climate change are warmer oceans and changing wind patterns, but a recent study published in Nature Climate Change explains how the chain reactions caused by a changing climate could dry out the Amazon rainforest and cause wetter conditions in the woodlands of Africa and Indonesia.
A study published in Nature Climate Change, shows rising Carbon Dioxide (CO2) levels interact with rainforests and contribute to asymmetrical rainfall pattern change across the tropics. Often in Earth system science, local environmental factors impact faraway regions by influencing the movement of moisture through the atmosphere.
"We have found that large-scale changes in rainfall can, in part, be attributed to the way tropical forests respond to the overabundance of carbon dioxide humans are emitting into the atmosphere, particularly over dense forests in the Amazon and across Asia." says James Randerson, UCI’s Ralph J. & Carol M. Cicerone Chair in Earth System Science.
Researchers predict a cascading effect that begins with the small structures on the underside of leaves, called stomata, that open and shut to allow plants to take in CO2 and release water vapour. When more CO2 is present, the stomata don’t open as widely, and less water is released. This process, multiplied across all the plants in the rainforest is what could cause the aforementioned atmospheric changes, affecting the way wind blows and the flow of moisture coming from the ocean.
"In many tropical forest regions, the moisture supplied by transpiration, which connects water underground at the root level directly to the atmosphere as it is pulled up to the leaves, can contribute as much as moisture evaporated from the ocean that rains back down at a given location - which is normal rainforest recycling," Says Gabriel Kooperman, the lead researcher in this study.
"But with higher CO2, trees and forests evaporate less moisture into the air, so fewer clouds are formed above the Amazon," Kooperman adds. This causes more rain to fall in the Andes mountain range with limited benefit to the rainforest in the Amazon basin.
The resulting droughts and forest mortality in the Amazon combined with the potential for increased flooding in other rainforests could impact biodiversity, freshwater availability and food supplies for for economically vulnerable populations.