The climate regulation service provided by miombo landscapes

Abstract

The African miombo woodlands are perhaps the world’s largest relatively unexploited but potentially arable land resource, located on a subcontinent where population growth remains high and demands for food security and development are pressing. This study aims to quantify the tradeoff between landscape transformation of various types and the climate regulation service provided by the miombo landscape. Net radiative forcing, expressed in terms of its carbon dioxide emission equivalent (CO2e) over a one century horizon was calculated for an intact (‘historical’) miombo landscape and for three hypothetical but observation-constrained derivatives: one developed through extensive subsistence farming; another by intensive, large-scale commercial farming; and one developed using ‘eco-agriculture’ improved smallholder techniques. The time course of net radiative forcing resulting from net carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emissions, from all significant sources (including production and decomposition processes, fires, cultivation, enteric emissions, termites, etc.) was assessed, as well as the net change in surface reflectance (albedo) for the four representative landscapes. It was found that the loss of climate regulation service was greatest when the entire landscape was converted to commercial agriculture, with conversion via subsistence extensification, offering the most protection for the climate regulation service. Conversion to eco-agriculture falls somewhere in between. If the loss of climate regulation service is expressed per unit agricultural production, the pattern is reversed, favoring commercial intensification as the choice mode of production. It was found that contrary to the conventional approach of evaluating the climate regulation service entirely on the basis of net carbon storage, the changes in other greenhouse gases (notably CH4, but also to a smaller extent N2O), and surface albedo made substantial contributions to the changes in the climate regulation service provided by miombo landscapes.