Forest protection is essential for reliable rainfall
There will not be many places in the world that have escaped the impact of the unusual droughts, floods and unseasonal temperatures experienced around the world recently.
These are often ascribed to the role of greenhouse gases, leading to climate change, but there are additional causes. An international research team has found that changes in vegetation cover, especially forest loss, pose a further threat.
For many parts of the world rainfall depends on what happens to land and water in distant countries. For example, a molecule of moisture that enters Europe from the Atlantic Ocean may fall as snow or rain, and be reevaporated to the atmosphere several times, before it reaches a rain-fed field in central Asia or China.
A new study published in the open-access journal Heliyon, aimed to identify the vulnerability of the atmospheric circulation processes – the drivers of the winds that maintain inland rainfall. Temperature and humidity are key and both heavily influenced by a region’s vegetation cover.
"We need nature, and we can defend it and achieve many other benefits at the same time."
The key finding is that high temperatures, along with a lack of suitable vegetation and resulting atmospheric moisture, can block the processes that sustain rainfall over land. In contrast, sufficient moisture being returned to the atmosphere sustains these processes and makes them more resilient.
The research team compared their theoretical predictions against several areas in the Northern Hemisphere, including Western Europe, North America and China. They indicate that current conditions are already close to the threshold where rainfall becomes unstable.
The research explains the apparent instability in the systems, leading to droughts and floods.
Large-scale solutions
The work underlines that forest loss, wetland drainage and other land use changes exacerbate these threats, while conserving and regenerating forests and wetlands reduces them. Furthermore, the results emphasise that these large-scale threats require large-scale solutions that recognise the interconnection that flow across national borders and continents.
The international research led by Dr Anastassia Makarieva at the Technical University of Munich, Germany, developed the fundamental ideas this research is based upon. The team identified a threshold in terms of temperatures and atmospheric moisture where the processes that maintain the dominant wind patterns cease – something the authors note has already been seen in some recent European summers.
Conserving forests and wetlands
Makarieva emphasises that Russia’s forests have a particularly important role for the Eurasian continent: “The region has been becoming progressively drier, suffering increasingly erratic wind and rain. One important solution is to protect and recover the region’s vast northern forests,” she said.
Professor Douglas Sheil from Wageningen University & Research in the Netherlands, a co-author on this study, says he is alarmed by the findings: “Our research shows that we are close to major disruption of the processes that keep much of the world green, pleasant and habitable.”
Sheil notes that while the study is technical, the results and implications are profound: “The conservationist in me is unsurprised that we have yet more evidence that we disrupt the natural work at our peril,” he says, "but there is also a positive message - we need nature, and we can defend it and achieve many other benefits at the same time.
"This study is about the reliable rain that we all depend on, but the solution is to maintain and regain forests and wetlands, that also protect biodiversity, store carbon, and provide many other vital goods and services.”