More Cities Means More Warming, Sure - But More Agricultural Land Means More Cooling?

small farm photo

photo: susteph via flickr.

A new study of the effect of land use changes on surface temperatures demonstrates what anyone who lives in a city intuitively knows: Urban areas are hotter than the surrounding countryside -- the heat island effect has been well demonstrated for a while -- but what's interesting is that researchers have found a switch from forest to agricultural land actually has a cooling effect:As to why conversion to agriculture can result in relative cooling, report co-author Eugenia Kalnay says increased evaporation is the presumed reason.

Carbon Storage of Forests Higher Than Fields
Again, that's on surface temperatures. In terms of carbon sequestration, intact forest has been demonstrated repeatedly to store more carbon than do monoculture agricultural fields -- particularly in the tropics.

hawaii forest photo

photo: roy.luck via flickr.
More Green Spaces Around Cities Can Help Mitigate Climate Change
But the greater point being made by researchers from Purdue University, and the Universities of Colorado and Maryland, is that local and regional strategies such as creating green spaces and other buffer zones around urban areas may be an effective tool in mitigating the effects of climate change. Also, the effect of land use conversion on rising surface temps is an underestimated component of global warming.

suburban sprawl photo

photo: Tim via flickr.
Land Use Changes Generally Result In More Warming
The study makes the following conclusions: 1) in general land use conversion often results in more warming than cooling; 2) deforestation results in surface warming, with the exception being conversion to agriculture; 3) conversion from agriculture generally results in warming, though no clear picture emerged from this research as to the effect of planting new forests; 4) urbanization and conversion to bare soils have the largest impact on warming surface temperatures.

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