Agriculture Reference
In-Depth Information
1 The Global Challenge for Soil Carbon
Steven A. Banwart*, Helaina Black, Zucong Cai, Patrick T. Gicheru,
Hans Joosten, Reynaldo Luiz Victoria, Eleanor Milne,
Elke Noellemeyer and Unai Pascual
Abstract
Soil carbon in the form of organic matter is a key component of the soil ecosystem structure. The soil
carbon content is an important contributing factor in the many flows and transformations of matter,
energy and biodiversity - the essential soil functions that provide ecosystem services and life-sustaining
benefits from soil. These goods and services include food production, water storage and filtration, car-
bon storage, nutrient supply to plants, habitat and biodiversity. Soil functions provide natural capital
as a means of production for the ongoing supply of the essential goods and services. Soil carbon con-
tent and soil functions are under threat worldwide due to resource demands and the increasing in-
tensification of land use. Land degradation is characterized by soil carbon losses, loss of soil structure
and associated loss of fertility, and the physical loss of bulk soil by erosion. Soil carbon accumulation
is associated with plant productivity, wet conditions that ensure water supply to vegetation and lack
of physical disturbance to the soil. Carbon accumulation is also associated with decreased organic
matter decomposition in the soil, created by cool conditions that reduce the rate of microbial activity
and wet conditions that create an O 2 diffusion barrier from the atmosphere and reduced aerobic micro-
bial respiration during organic matter decomposition. The environmental conditions for the accumu-
lation of soil carbon also provide important clues to management approaches to reverse soil carbon
losses and to increase soil carbon content under widely different environmental conditions around the
world. Soil management strategies can be developed from the natural cycling of soil carbon, by redu-
cing physical disturbances to soil, enhancing vegetation cover and productivity and through improved
water management. These approaches are essential in order to prevent and reverse the loss of soil
functions where land is degraded and to enhance soil functions where actively managed land is under-
going intensification of use. Improved soil carbon management provides an important opportunity in
land management worldwide, to meet increasing resource demands and to create resilience in soil
functions that arise from the intense pressures of land use and climate change.
Introduction
2013). This enormous demographic pres-
sure creates four major global challenges
for Earth's soils over the coming four
decades.
By 2050, the world's population is ex-
pected to reach 9.6 billion (United Nations,
 
 
 
 
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