Abandoned farmland in Western Europe is up to 1.8 degrees Fahrenheit COOLER than when it was being farmed. Trees providing shade and more moisture in the atmosphere are the main source of these cooling effects. The evidence comes from a newly published paper. titled "Predominant regional biophysical cooling from recent land cover changes in #Europe."
This means rewilding could play an important role in partially offsetting rising temperatures across Europe, according to a new study.
Rewilding aims to return land to a more natural state. This is done by allowing #nature to take its course. Activists call for #rewilding to be encouraged in order to save essential areas and species. They also call for reintroducing species that have disappeared as a result of man’s actions.
Satellite images and atmospheric studies show temperatures dropped up to 1.8 degrees on abandoned farmland. These temperature drops were directly attributed to #tree growth and extra moisture that redirected solar energy instead of it being absorbed in the ground as well as absorbing greenhouse gases like #CO2.
A team of scientists, led by Francesco Cherubini of the Norwegian University of Science and Technology, found that in Western Europe the ground temperature on abandoned #farmland could be up to 1.8 degrees Farenheit cooler than it had been with active farms.
There was greater evapotranspiration, the process through which water evaporates from wetlands, tree leaves, and other moisture sources, decreasing the amount of #solar energy absorbed by the ground.
‘The message is quite clear: Abandoned cropland—or land cover change more generally—and its role in regional climate can help to us adapt and mitigate the effects of climate change,’ Cherubini said.
‘And by improving agricultural systems, we can free up land for multiple uses.’
The science team compiled satellite data from the European Space Agency collected between 1992 and 2015 and identified eight general #landuse categories: evergreen needleleaf forest, deciduous broadleaf forest, open shrubland, cropland, urban and built-up, cropland/natural vegetation mosaic, wetland, and grassland.
Their computer program modelled the changes in climate over that same time, based on real atmospheric observations. They then compared the model's results with an array of different regional #climate studies to ensure their numbers were accurate.
The team said a variety of factors contributed to the cooling phenomenon, including more trees to absorb CO2 and deflect sunlight, meaning less solar energy was absorbed by the ground
In all, they found more than 25 million hectares of agricultural land had been abandoned across Europe during the 24 years they had data for, roughly the same size as Switzerland.
The main causes of land abandonment were socioeconomic, according to the team.
‘We saw this especially in the former Soviet Union after the fall of the (Berlin) Wall, because farmers were exposed to agricultural trade and international markets.’
Other studies have focused on tree growth, which helps take CO2 out of the air, but Cherubini and his team wanted to focus on a more holistic set of metrics, including water evaporation rates, humidity levels, and soil moisture.
Cherubini said that in western Europe, policymakers could have "specific planning and incentives for revegetation of open land, considering the local cooling benefits as a synergy of global climate change mitigation,"
Interestingly, the effect didn’t hold true for Eastern Europe, where the team saw land temperatures actually rise on abandoned farmland. The team attributed this to a dryer climate, which meant less water was available for evaporation and more energy from the sun was absorbed directly by the land, which became even hotter without regular irrigation and watering, raising surface temperatures. This suggests that different land management strategies for different regions would be called for.
‘The ambition here is to have land management planning, where you can tackle the global challenges of carbon storage through land management, combined with strategies that have local cooling benefits,’
Very specifically Cherubini said in relation to #climatechange:
"We are already at a mean warming of about 1.8 degrees C on the land, and we will be about 3 degrees on the land even if we are successful at stabilizing the average global temperature at 1.5 degrees C," he said. "That means we need to take action to adapt to a warming climate, and land use planning is one action that can bring local cooling benefits."
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More information: Bo Huang et al. Predominant regional biophysical cooling from recent land cover changes in Europe, Nature Communications (2020). DOI: 10.1038/s41467-020-14890-0