Direct Climate Impacts of Commercial Agricultural Expansion

Transcription

1 Direct Climate Impacts of Commercial Agricultural Expansion Michael T Coe The Woods Hole Research Center Commercial Agriculture in Tropical Environments Third Annual International Food Security Symposium University of Illinois April 4, 2017

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3 Global meat demand Global soy Imports Increasing global demand for meat Drives increasing meat and grain production for feed Brazil has been at fore-front of this expansion

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5 Soy and Corn exports from Mato Grosso Corn Soy

6 Cumulative deforestation

7 Cumulative deforestation 850 Cumulative loss (thousand km 2 ) Biome Amazon Cerrado Year

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9 How are forests important for the climate system? Forests important for carbon balance and climate ~ 15% of all CO 2 put into atmosphere is from deforestation Ending deforestation keeps CO 2 out of atmosphere Reforestation takes excess CO 2 from atmosphere Forests also have very direct affect on regional climate Recycle water to atmosphere Maintain low surface albedo and high net radiation Support high convective activity and rainfall particularly at beginning and end of wet season

10 Incoming precipitation and net radiation Precip Rnet = ET + R = ET + H Vegetation is a key part of the transfer of energy and water back to atmosphere Coe et al., 2016; Panday et al,. 2015; Silverio et al., 2015

11 Coe et al., 2016; Panday et al,. 2015; Silverio et al., 2015

12 Coe et al., 2016; Panday et al,. 2015; Silverio et al., 2015

13 Coe et al., 2016; Panday et al,. 2015; Silverio et al., 2015

14 Spracklen and Garcia-Carreras, 2015; Costa et al., subm.

15 Xingu MaToPiBa

16 Upper Xingu 176,000 km 2 area Forested indigenous reserve surrounded by mosaic landscape. Compared values of evapotranspiration and land surface temperature from MODIS for native vegetation, crops and pastures, for period Silverio et al., 2015

17 Intact forests send about about 3/4 of incoming solar radiation and precipitation back to atmosphere Equivalent to ~1300 mm/yr or ~100 W/m2 Throughout much of long dry season Maybe use Panday et al.,2015; Silverio et al., 2015

18 Soy and pasture evapotranspire at the same rates as forest during growing season Silverio et al., 2015

19 Soy and pasture evapotranspire at the same rates as forest during growing season But not during the dry season Water is trapped in soil because there are no active roots Annual evapotranspiration reduced by ~25-30% (pasture and soy respectively) Sensible heat increased 6-10% Rnet decreased by 12-18% Land surface temperature C hotter than the forest Silverio et al., 2015

20 Upper Xingu Surface Temperature outside reserve is 3C warmer and increasing Silverio et al., 2015

21 Upper Xingu Flux of water to atmosphere decreased by 6% Silverio et al., 2015

22 Agricultural expansion in Cerrado 2 million ha brought into mechanized agriculture in MaToPiBa region from % in native Cerrado, remainder from existing pastures km 3 /yr less evapotranspiration over that decade (~-3%) Spera et al. 2016

23 Agricultural expansion in Cerrado Government projections are for an additional nearly 3 million ha of crop expansion in this region 2001 Equals an additional evapotranspiration decrease of about 4.5km 3 Spera et al. 2016

24 Eva et al., 2003 Present day

25 Soares-Filho et al., with governance

26 Soares-Filho et a., business as usual

27 Modeling Land Surface Processes and Atmospheric Feedbacks Are future atmospheric feedbacks to rainfall of potentially important scale? What are consequences for ecosystem services? Coe et al., 2009, Oliveira et al., 2013, Stickler et al., 2013

28 BAU 2050 Regional rainfall decrease of 15% Xingu Tocantins Coe et al., 2009

29 Rainfall decrease has consequences for ecosystem services Xingu 30% decrease in crop yield in both basins 30% decrease in power potential of Xingu Tocantins Oliveira et al., 2013 Stickler et al., 2013

30 Conclusions: Deforestation fundamentally shifts energy/water balance (ET, ds, Q, Rnet, H, T). Large areas of Cerrado and Amazon have been deforested measurable changes to energy and water balance have occurred. Deforestation continues both, legal and illegal. Deforestation is consistent with recent observed changes in rainfall at end of dry season. Future climate and productivity of the region will depend on how much deforestation rates can be curbed or reversed.

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