Cascading Moisture Recycling

node · earth · Amazon Basin

The refinement that turns moisture recycling from an average into a chain. Simple recycling asks what fraction of rainfall at a point came from evapotranspiration somewhere in the basin. Cascading recycling asks how many times the same water has done it: a molecule evaporated from the Atlantic may fall in Para, be transpired, fall again in Amazonas, be transpired again, and reach Acre or Rondonia only on its third or fourth landfall. Zemp and colleagues quantified this cascade and drew the consequence that makes it dangerous. If recycling is a chain, then forest loss anywhere upwind shortens the chain everywhere downwind, and the loss is not proportional to the area cleared - it compounds. Their modelling found that vegetation-atmosphere feedbacks can substantially amplify forest loss beyond what deforestation and climate change would cause independently, with the southern and southwestern basin most exposed. This is the specific reason that "how much forest is left" is a worse question than "where is the forest that is left".