  Along with the accumulation of atmospheric carbon dioxide, the loss of
primary forests and other natural ecosystems is a major disruption of the Earth
system causing global concern. Quantifying planetary warming from carbon
emissions, global climate models highlight natural forests' high carbon storage
potential supporting conservation policies. However, some model outcomes
effectively deprioritize conservation of boreal and temperate forests
suggesting that increased albedo upon deforestation could cool the planet.
Potential conflict of global cooling versus regional forest conservation could
harm environmental policies. Here we present theoretical and observational
evidence to demonstrate that, compared to the carbon-related warming, the model
skills for assessing climatic impacts of deforestation is low. We argue that
deforestation-induced global cooling results from the models' limited capacity
to account for the global effect of cooling from evapotranspiration of intact
forests. Transpiration of trees can change the greenhouse effect via small
modifications of the vertical temperature profile. Due to their convective
parameterization (which postulates a certain critical temperature profile),
global climate models do not properly capture this effect. This
parameterization may lead to underestimation of warming from the loss of
evapotranspiration in both high and low latitidues, and therefore, conclusions
about deforestation-induced global cooling are not robust. To avoid deepening
the environmental crisis, these conclusions should not inform policies of
vegetation cover management. Studies are mounting quantifying the stabilizing
impact of natural ecosystems evolved to maintain environmental homeostasis.
Given the critical state and our limited understanding of both climate and
ecosystems, an optimal policy would be a global moratorium on the exploitation
of all natural forests.
