Global climate change caused by rising levels of carbon dioxide (CO2 ) and other greenhouse gases is recognized as a serious environmental issue of the twenty-first century. The role of land use systems in stabilizing the CO2 levels and increasing the carbon (C) sink potential has attracted considerable scientific attention in the recent past, especially after the Kyoto Protocol to the United Nations Framework Convention on Climate Change (UNFCCC). The Kyoto Protocol recognizes the role of afforestation, reforestation, and natural regeneration of forests in increasing the C storage capacity of terrestrial ecosystems. The post-Kyoto Protocol discussions on climate change are also heavily oriented towards an agenda on mitigating the rising atmospheric CO2 levels through C sequestration in terrestrial vegetation systems.
Although the pristine natural forest ecosystems represent the largest vegetation and soil C sinks, a considerable extent of this has already been lost especially in the less developed and developing countries of the world. It is unlikely that these degraded and deforested sites will be returned to natural forest cover. The need for transforming some of the lower biomass land uses (such as arable croplands and fallows) to carbon-rich tree based systems such as plantation forests and agroforestry therefore assumes significance. Agroforestry systems (AFS) spread over one billion ha in diverse ecoregions around the world have a special relevance in this respect. These woody perennial-based land use systems have relatively high capacities for capturing and storing atmospheric CO2 in vegetation, soils, and biomass products.
According to the Intergovernmental Panel on Climate Change, AFS offer important opportunities of creating synergies between both adaptation and mitigation actions with a technical mitigation potential of 1.1–2.2 Pg C in terrestrial ecosystems over the next 50 years. Additionally, 630 million ha of unproductive croplands and grasslands could be converted to agroforestry representing a C sequestration potential of 0.586 Tg C/yr by 2040 (1 Tg=1 million tons). The total C storage in the aboveground and belowground biomass in an AFS is generally much higher than that in land use without trees (i.e. tree-less croplands) under comparable conditions. Various agroforestry practices such as alley cropping, silvopasture, riparian buffers, vi Preface parklands, forest farming, homegardens, and woodlots, and other similar land use patterns have thus raised considerable expectations as a C sequestration strategy in both industrialized and developing countries