precipitation. How could the biotic pump theory connect to this? Victor Gorshkov and Anastassia Makarieva: This data, as well as the data on the Nazca civilization in Peru, are in agreement with the biotic pump concept. It is noteworthy that the Yucatan peninsula is a relatively small region with maximum distance from coast never exceeding a thousand kilometers. This means that even so close to the ocean, massive deforestation can cause a significant precipitation decline. The proposed explanation (see article: Evidence mounts that Maya did themselves in through deforestation) based on a slight change in albedo after deforestation and a corresponding decrease in solar energy available for convection does not make sense to us (although as we understand this work has not yet been published so we could not read it in detail). The power of atmospheric circulation does not exceed around 1 percent of solar power. It is not limited by solar radiation, but by the flux of potential energy available for conversion to the kinetic energy. The conventional paradigm associates this potential energy with temperature-related buoyancy. That is, to put things simply, if you do not have a temperature difference, you do not have a circulation, all other things (including solar energy) being the same. We propose a different source of potential energy associated with water vapor removal from the gas phase: after the Mayan forests were destroyed, evaporation and condensation ceased to occur over the Yucatan peninsula (irrespective of how its albedo changed). The result was that the low pressure zone was no longer there and moist air ceased to come to the Maya from the ocean. Generally, the biotic pump theory calls us to re-analyze the historical evidence associated with land cover change and the changes in the precipitation regime. Mongabay: How do you see deforestation in the Amazon as impacting regional precipitation? Victor Gorshkov and Anastassia Makarieva: According to recent analyses, during 1973-2003 precipitation in the Amazon River basin was declining at a rate of 0.3 percent annually, which means a trend of about 10 percent for the entire period. This does not include the most recent devastating droughts of 2005 and 2010. In the meantime, deforestation in the basin has amounted to about 30 percent during the same period. Deforestation mostly disturbed southern and south-eastern parts of the basin, where the precipitation/evaporation is less than in the basin core. Assuming that the total biotic pump intensity is a function of the integral of local precipitation over the total forest-covered area, one can conclude that the decrease in precipitation intensity is of the same order of magnitude as the degree of biotic pump deterioration. As deforestation marches to the interior of the basin and affects the ever more productive forests with the most precipitation, the disruption of the water cycle in the basin will increase disproportionately. Mongabay: How do you think widespread deforestation will effect the hydrological cycle of places like the Indonesian islands? Given their smaller size, do they need the biotic pump? Devastated rainforest landscape in Borneo. Indonesia has one of the highest rates of