Soil Carbon Transition Curves: Reversal of Land Degradation through Management of Soil Organic Matter for Multiple Benefits - Soil Carbon: Science, Management and Policy for Multiple Benefits - page 26

3 Soil Carbon Transition Curves:
Reversal of Land Degradation through
Management of Soil Organic Matter for
Multiple Benefits
Meine van Noordwijk*, Tessa Goverse, Cristiano Ballabio,
Steven A. Banwart, Tapas Bhattacharyya, Marty Goldhaber,
Nikolaos Nikolaidis, Elke Noellemeyer and Yongcun Zhao
Abstract
Soils provide important ecosystem services at the local, landscape and global level. They provide the basis
for crop, livestock and forestry production and help mitigate climate change by storing carbon. With expect-
ations of a growing bioenergy supply to meet global energy demand added to the imperative to feed a global
population of 9 billion people by mid-century and beyond, coupled with higher per person food demands
than currently provided, the challenges to keep agricultural and rangeland soils healthy and productive are
daunting. In this paper, we explore the existence of a common pattern in the use of soils under increasing
demand for productivity - here described as a soil carbon transition curve : a rapid decline of soil carbon due
to human clearing of natural vegetation for agricultural land use and management practices, followed by a
'crisis' phase of diminished soil fertility and finally by recovery once agricultural practices improve. We test
this pattern in its ability to convey the impact of major land-use changes on soils, with examples from arable,
grazing and forest land in different parts of the world. The initial stage of the curve represents a trade-off
between extractive productivity (growing crops, extracting biomass, excessive burning and grazing) on the
one hand and the farm-level, landscape plus global benefits of soil carbon storage on the other hand, based
on the loss of an initial endowment of soil organic matter. The second, turnaround stage of the curve often
following a crisis tends to be driven by locally relevant loss of ecosystem services, manifest as flooding,
pests and crop diseases, erosion and nutrient deficiencies. In the final, recovery stage, local, landscape and
global benefits coincide, and synergy between local and global stakeholders' interests dominates the trajec-
tory. In mineral soils used for crop production, recovery generally requires a change in tillage and residue
management, crop-livestock integration and/or a return of (agroforestry) trees to agricultural landscapes,
plus maintaining adequate nutrient levels. In grasslands, a control of grazing pressure is generally needed
in order to recover the vegetation. While global soil carbon storage is linked positively to other ecosystem
functions in the recovery stage, the magnitude of the services involved differs substantially between soil
types. Incentives for carbon emission reduction and prevention may be drawn towards a small fraction of
soils with very high emission potential, especially peatlands, while incentives to maintain or enhance soil
carbon storage will be most effective for soil in Stages I and II of the transition curve. Increased carbon
storage to mitigate climate change, however, should not be considered the main purpose for improved soil
organic carbon management but could be seen as a co-benefit of actions that seek local and watershed-
level benefits from a full set of improved ecosystem services provided by soil organic carbon.