It is well known that they play key role in absorbing greenhouse gas emissions, but recently science has discovered that forests are even more important to the climate than we thought.
This was demonstrated by a report by WRI, the World Resources Institute, which highlighted the importance of non-carbon related effects that forests have on the climate and beyond. These are in particular biophysical processes that influence the transfers of energy and humidity in the atmosphere, scientists explain: actions that among other things contribute to our food and water securityprotect ours salute and improve our ability to adaptation to a warming planet.
Taking these processes into account allows us to review estimates on the role of forests and their impact on the climate, as well as the severe risks associated with deforestation. In fact, the removal of forest cover, especially in the tropics, causes an increase in local temperatures and influences rainfall patterns, aggravating the local effects of global warming, with worrying effects also on human health and agricultural productivity.
“Policy makers should urgently recognize and address the full range of climate regulation services of forests through institutions operating on relevant scales – warn the researchers of the World Resources Institute -, including the United Nations Framework Convention on Climate Change (UNFCCC), institutions for regional cooperation and national agencies dealing with agricultural productivity and public health”.
How do forests affect climate?
The contribution of forests inabsorb carbon dioxide emissions it is essential to achieve the climate goals we have set ourselves, and indeed it will also be necessary to restore the forests that we have damaged or destroyed so far.
But forests also have other effects, often overlooked so far, which are not related to emissions but have important local, regional and global implications. Among these we find for example the albedo, the evotraspiration or the release of aerosols.
The albedo indicates the possibility of reflect solar energy from a surface. Light colored surfaces return a large part of the sun’s energy to the atmosphere and can have a cooling effect (high albedo), while dark ones absorb the sun’s rays and can heat up (low albedo). The tree cover usually dark green absorbs more energy of snow cover, cultivated land or bare soil, warming the air.
Evapotranspiration, or the role of trees in releasing moisture into the air, produces a cooling effect. This occurs when water evaporates from the surface of the leaves, and how a natural conditioner manages to cool the surrounding air and the earth’s surface. This process also significantly affects cloud generation.
Aerosols they are tiny particles released by forests, such as pollen but also other chemical compounds. These particles and compounds interact with the atmosphere in complex ways, for example by changing ozone and nitrate concentrations and even influencing the color of clouds.
The effects of deforestation
Deforestation has huge impacts on the climate. The best known concerns the emissions, and is linked on the one hand to those that the destroyed forest stops absorbing, on the other to those generated by the products of deforestation, such as burning wood. But there are other effects that are not related to carbon and depend on various factors, the main one being the latitude.
The forests located at tropical latitudes have particularly important effects on the climate not only with regard to carbon dioxide emissions, but also due to the high rates of evapotranspiration and their ability to stimulate the cloud cover.
Large tracts of tropical forests, such as those in the Amazon and Congo basins, capture moisture from the atmosphere as it falls as rain, and then release it through evapotranspiration. Large-scale deforestation can disrupt this cycle, exacerbating the Drought in leeward areas even hundreds of kilometers away from forests. For example, researchers estimate that forests in Brazil provide 13 to 32 percent of the annual rainfall in the leeward countries of Bolivia, Paraguay, Uruguay and Argentina. Deforestation in Brazil can therefore be a major contributor to drought in these countries.
In the tropics, the direct effects of deforestation on human populations are also of particular concern local temperatures, already so high as to make any further warming even more risky. According to some studies, when tropical forests are destroyed to make way for cultivated land, daytime temperatures can locally increase by more than 7 degrees. Currently this overheating already poses a serious threat to the people’s health, extremely exposed to heat stress which can prove lethal, and for the crop productivity.
According to scientists, when the non-carbon effects of tropical deforestation are taken into account, its estimated contribution to global warming increases by 50% compared to the carbon effects alone. Protecting these forests, therefore, provides a huge global cooling “bonus” that current climate and environmental policies are not taking into account.
The boreal forests, on the other hand, have an overall warming effect because their canopy is much darker than the underlying snow, and therefore absorbs solar energy instead of reflecting it back into space. This effect of heating albedo affects climate far more than carbon removal and evapotranspiration-related cooling of boreal forests due to their slow growth rates. Of course, experts point out, this doesn’t mean that to meet climate goals we would have to remove boreal forest cover, which provides many other all-important benefits, such as beneficial local climate regulation.
Rosina Kaiser da Pixabay’s photo
What are the consequences if we ignore the non-carbon effects of forests?
The policies of mitigation and adaptation to the climate – i.e. measures aimed at countering the further increase in temperatures and tackling the now inevitable effects of the climate crisis – do not yet take into account the impacts of forests that are not linked to carbon. As a result, they currently systematically underestimate their own climate services not consequences of deforestationand lead to an unequal sharing of responsibilities and resources for climate action.
For example, national climate accounting that is based only on the role of forests in absorbing emissions leads to overestimating the cooling effects associated with them in higher latitude countries and underestimate them in tropical countries.
Furthermore, there is a lack of intergovernmental institutions dealing with the transboundary effects of deforestation on rainfallso affected populations in leeward countries cannot represent their interests in the decision-making processes of nations where deforestation occurs.
The Not just carbon report of the World Resources Institute is available, in English, at this link.
