MadSci Network: Environment

Re: how does global warming affect world plant growth and co2 absorption

Date: Tue Sep 13 01:44:38 2005
Posted By: Alex Barron, Graduate Student, Ecology(Biogeochemistry)
Area of science: Environment
ID: 1124856454.En

Andrew -
Based on what we know about the earth’s climate system, it seem likely 
that some areas may experience longer growing seasons and/or increased 
productivity as a result of global warming but that this effect will be 
far too small to slow global warming enough.  Both warmer temperatures and 
elevated CO2 can be good for plants, especially under ideal lab 
conditions.  However, other factors may limit or even reverse this effect 
in the real world.  Global warming is likely to shift rainfall patterns, 
which may lead to drought (and possibly more wildfires) in many areas.  
Plants also need nutrients like nitrogen and phosphorus to grow - if there 
aren’t enough of these nutrients around, plants won’t increase in 
productivity.  Finally, other changes that come with burning fossil fuels 
(such as air pollution) reduce the productivity of crops and natural 
Most importantly, the increases in productivity in some areas (negative 
feedbacks) will not be enough to offset our continued emissions of 
greenhouse gasses.  Most of the current models already include our best 
guess for the productivity gains you hypothesize and they still predict 
that both CO2 concentrations and temperature will continue to rise if we 
don’t cut our greenhouse gas emissions.  Increased warming in places like 
polar regions 
may increase the growth of plants there but can also melt permafrost and 
trigger the release of carbon stored in the soil.  These “positive 
feedbacks” could increase CO2 and temperature far more rapidly than the 
productivity gains in other areas could slow things down.  Overall, we 
can't count on increased plant productivity to solve global warming for us.

If you’re really interested, the most recent scientific consensus can be 
found at: although 
evidence for global warming has gotten even 
stronger since this report was published (2001).  The summaries for policy 
makers contain lots of details.

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