Tropical forest conservation can relax climate constraints on neighboring agriculture productivity

Transcription

1 Tropical forest conservation can relax climate constraints on neighboring agriculture productivity Avery Cohn (with Graham Jeffries, Britaldo Soares Filho, Nishan Bhattarai, and John Duncan) Tufts University 1

2 Outline Using evidence from Brazil, I show that climate change, primarily from deforestation, is already substantially constraining neighboring agricultural productivity in tropical forest frontier regions We found deforestation increased mean annual maximum temperature of some neighboring agricultural regions up to 5 deg C and increased extreme heat exposure by up to 150%, a potent cause of lost agricultural productivity These estimates allow us to calculate that, conversely, forests are of great value in regulating the climate of neighboring croplands A strong agribusiness case for forest conservation is emerging, particularly under scenarios of high agricultural expansion, deforestation, and GHG emissions 2

3 Climate change is already constraining tropical agriculture But, the source isn t primarily GHGs. Minor tropical climate change from global GHGs has already occurred. But in forest frontiers, these changes add to a much larger climate change source--physical, localized changes from land use change, especially the conversion of forests to pasture and cropland. Forest loss can cause: Local to continental scale changes in the quantity and distribution of precip. Increased temperatures 3

4 We sought to estimate dispersive cooling from deforestation Above canopy temperature Under canopy cooling Below canopy temperature Dispersive cooling Adapted from McDonald et al Canopy cooling distance Dispersive cooling distance 4

5 Dispersive cooling is highly localized and often far from weather stations Stations per 1000km^2 just ~80 weather stations in Brazilian Amazon an area 2/3 the size of the U.S. 5

6 We relied on land surface temperature of forests detected by satellites as a proxy for near surface air temperature MODIS AQUA SATELLITE 6

7 We modeled warming of patches of undisturbed forests caused by changes in forests 1-2km, 2-4km, 4-10km, 10-25km away. Our model is causal, controlling for space fixed effects, time fixed effects, cloudiness, and several other controls. 7

8 We found roughly 5 deg C warming from deforestation within 25km. 8

9 Warming was concentrated in Amazon-cerrado transition zone. This is shifting extreme heat into forest fringe 9

10 Agricultural expansion is causing the warming and increasing its own climate risk 10

11 Standing forests cool agriculture. Forest value for neighboring farms through EDD( ) FV = σ ring x year PV jt PV ijt = EDD ij km j 2 X lost_yield (t/ha) EDD X Ag area ijt(ha) ring X value t (2012$) pdxn(t) i is sentinel forest location j is ring radius t is growing year ~0.5 2km, 4km, 10km, & 25 km ~1%/day above 30 C, Schlenker & Roberts, 2009 Mean of 11% for stratified (25km) random sample of forest w/i 5km of agriculture ( ), Spera et al Soy producers price Chicago Board of Trade 11

12 Climate reg. value (CRV) of forests highest in agfrontier, particularly emerging frontier, Matopiba 12

13 CRV rivals cropland value and carbon value of forests 13

14 Acknowledgments We thank Michael Coe, Reem Hajjar, Marcia Macedo, Dan Miller, Nathan Mueller, and Sally Thompson for comments and Anaya Hall for research assistance. Support for Cohn, Duncan, and Bhattarai came from the Dutch Ministry of Economic Affairs, Grant #