The C stored in soils is nearly three times that in the aboveground biomass and approximately double that in the atmosphere. Reliable estimates have been difficult to obtain due to a lack of global data on kinds of soils and the amount of C in each soil. With new data bases, our study is able to provide more reliable data than previous estimates. Globally, 1576 Pg of C is stored in soils, with ~ 506 Pg (32%) of this in soils of the tropics. It is also estimated that =40% of the C in soils of the tropics is in forest soils. Other studies have shown that deforestation can result in 20 to 50% loss of this stored C, largely through erosion. '"THE EQUILIBRIUM OF C on earth is a function of three J. reservoirs, the oceans, atmosphere, and terrestrial systems. These three reservoirs are in a dynamic equilibrium, each interacting and exchanging C with the other. A fourth reservoir, the geological reservoir, is estimated to have 65.5 x 10 6 Pg (Kempe, 1979) and is a permanent sink. A small fraction (=4000 Pg) of the geological sink is present as fossil fuels from which C release takes place as a result of mining activities of man. The relative amounts of C stored in each of these reservoirs is given in Table 1. Recent concerns about the "greenhouse effect" and damage to the ozone layer have resulted in more concerted studies on the quantities, kinds, distributions, and behavior of C in the different systems (Johnson and Kerns, 1991). Although the purpose of many of
Anticipated advances in biotechnology and sustainable land management, in combination with the availability of high-quality lands, suggest a level of food production that will sustain twice the current global population. However, lack of political will, insufficient investments in modern agriculture, and a general apathy to the tenets of sustainable land management threaten food security in Third World countries, and in some, contribute to poverty and famine. From a global land-productivity point of view, the specter of Malthusian scenarios seems unwarranted. Sadly, however, local and regional food shortages are likely to continue to occur unless mechanisms for equitable food distribution, effective technical assistance, and infusions of capital for infrastructure development are implemented in some developing countries.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.