Another Example Of The Importance Of Land Management Within The Climate System – A New Paper By Ridgwell Et Al 2009 Entitled “Tackling Regional Climate Change By Leaf Albedo Bio-Geoengineering”

There is an interesting New York Times article by Henry Fountain titled “More-Reflective Crops May Have Cooling Effect” [and thanks to Matei Georgescu for alerting us to it!]. The article states that

“Andy Ridgwell and colleagues at the University of Bristol in England have another idea, one they call bio-geoengineering. Rather than developing infrastructure to help cool the planet, they propose using an existing one: agriculture.

Their calculations, published in Current Biology, suggest that by planting crop varieties that reflect more sunlight, summertime cooling of about 2 degrees Fahrenheit could be obtained across central North America and a wide band of Europe and Asia.”

This NY Times article is based on the paper

Andy Ridgwell1,Joy S. Singarayer,Alistair M. Hetherington andPaul J. Valdes: 2009 “Tackling Regional Climate Change By Leaf Albedo Bio-geoengineering“. Current Biology, Volume 19, Issue 2, 146-150, 15 January 2009

The abstact of this paper reads

 “The likelihood that continuing greenhouse-gas emissions will lead to an unmanageable degree of climate change [1] has stimulated the search for planetary-scale technological solutions for reducing global warming [2] (geoengineering), typically characterized by the necessity for costly new infrastructures and industries [3]. We suggest that the existing global infrastructure associated with arable agriculture can help, given that crop plants exert an important influence over the climatic energy budget [4,5] because of differences in their albedo (solar reflectivity) compared to soils and to natural vegetation [6]. Specifically, we propose a bio-geoengineering approach to mitigate surface warming, in which crop varieties having specific leaf glossiness and/or canopy morphological traits are specifically chosen to maximize solar reflectivity. We quantify this by modifying the canopy albedo of vegetation in prescribed cropland areas in a global-climate model, and thereby estimate the near-term potential for bio-geoengineering to be a summertime cooling of more than 1C throughout much of central North America and midlatitude Eurasia, equivalent to seasonally offsetting approximately one-fifth of regional warming due to doubling of atmospheric CO2[7]. Ultimately, genetic modification of plant leaf waxes or canopy structure could achieve greater temperature reductions, although better characterization of existing intraspecies variability is needed first.”

The conclusion reads

“Increasing canopy albedo of vegetation in designated cropland areas in a global climate model by 20% (0.04) drives a >1C reduction in summertime surface air temperatures in a wide latitudinal band spanning North America and Eurasia. Genetic modification or selective breeding of crop plants for specific leaf-surface properties and canopy structure could provide further mitigation of surface warming. Because the main investment is in research and field trials, the relatively low cost of implementation of crop albedo bio-geoengineering makes it potentially very attractive when compared to the equivalent costs of geoengineering or carbon sequestration. However, there is a clear need for more research into characterizing the variability in albedo that exists between the different variants and strains of common crop plants to underpin any such undertaking. Changes in crop reflectivity must also not significantly
negatively impact on crop yield through excessive reduction in the absorption of photosynthetically active radiation by chloroplasts under nonsaturating light conditions. Overall, bio-geoengineering could fulfill a role as a temporary measure for reducing the severity of agricultural and health impacts of heat waves in the industrialized North, but on a global scale, it has limited effectiveness for the mitigation of future climate change and cannot substitute for CO2 emissions reductions. Furthermore, although a prominent increase in summertime soil moisture in the southern states of the U.S. also occurs, soil moisture changes show no simple spatial relationship to the prescribed albedo changes, illustrating the difficulties in predicting the response of the global climate system to deliberate modification, particularly with respect to rainfall patterns. The potential for significant regional inequity in soil-moisture changes poses important geopolitical questions.”

This is yet another example of the importance of the human management of the landscape within the regional climate system. A summary of this effect, as well as documenting that advertant and inadvertant land management is not a ‘temporary measure” and that this management has significant consequences even on the global scale, was published in the articles

Pielke Sr., R.A., 2005: Land use and climate change. Science, 310, 1625-1626

Pielke Sr., R.A., G. Marland, R.A. Betts, T.N. Chase, J.L. Eastman, J.O. Niles, D. Niyogi, and S. Running, 2002: The influence of land-use change and landscape dynamics on the climate system- relevance to climate change policy beyond the radiative effect of greenhouse gases. Phil. Trans. A. Special Theme Issue, 360, 1705-1719.


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