Climate Change and Soil Degradation Mitigation by Sustainable Management of Soils and Other Natural Resources
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Soil, an important component of land, has numerous functions and ecosystem services essential to all terrestrial life. Soil degradation, decline in its capacity to support functions and provide ecosystem services, is caused by accelerated erosion, salinization, elemental imbalance, acidification, depletion of soil organic carbon (SOC), reduction in soil biodiversity, and decline in soil structure and tilth. Desertification, a sub-set of degradation, specifically refers to decline in soil quality and functions in arid climates. Climate change affects and is affected by soil degradation through a positive feed back due to increase in mineralization of SOC pool and the radiative forcing. Desertification may lead to a net increase in temperature despite change in albedo of the denuded surface. Feedbacks and threshold amplify the risks of degradation, and the projected climate change may exacerbate all four types of drought (i.e., meteorological, hydrological, pedagogical, and ecological). The mutually reinforcing positive feedbacks between soil degradation and climate change are strongly influenced by social, economic, political, and cultural factors. There exists a strong link between poverty, desperateness, and societal collapse on soil degradation and climate change. Restoration of degraded and desertified soils, converting marginal agricultural areas to rangeland and forest land, and adoption of recommended management practices have a large technical potential to sequester carbon and off-set anthropogenic emissions, improve the environment, and enhance and sustain agronomic productivity. Important among recommended management practices are using conservation agriculture and mulch farming, establishing cover crops, adopting strategies of integrated nutrient management, and those which create positive C and nutrient budgets and soil/water conservation within a watershed. Long-term research is needed which is hypothesis-driven, uses modern innovative research and modeling tools, is based on community involvement, and provides decision support systems to policy makers and land managers.
KeywordsSoil resilience Degradation Desertification Climate change Natural resources management Soil restoration Watershed management Carbon sequestration
Available water capacity
Community-based natural resource management
Decision support system
Integrated nutrient management
Life cycle analyses
Natural resource management
Net primary productivity
Recommended management practices
Soil organic carbon
West Asia North Africa
Land refers to the part of Earth’s surface that is not covered by water, and is a topographically or functionally distinct tract. The land domain includes everything from top of the atmosphere to the bedrock and beneath (in Latin = Cuius est solum eius est usque et ad inferos). Thus, land consists of atmosphere, vegetation, water, terrain, and all biota above the surface and ground water and minerals below the surface. Soil is an important component of land. Soil is a four dimensional body (length, width, depth, and time), at the interface between atmosphere and the lithosphere, and essential to all terrestrial life. Functionally, soil is also geomembrane of the earth, protective filter, buffer, and mediator of energy, water and biogeochemical compounds, reservoir of a very large germpool, and archive of planetary history.
Soil degradation implies decline in its capacity to provide ecosystem services (ESs) of interest to humans and useful to nature’s functions. Principal processes of soil degradation are erosion, salinization, nutrient and carbon (C) depletion, drought, decline in soil structure, and tilth. Examples of ESs provided by soil include ecological/supporting (biomass production, nutrient cycling), regulating (water purification and flow, C sequestration, temperature fluctuations), provisional (food, fiber, fuel, and forages), and cultural (aesthetical, spiritual, and cultural). Erosion-induced degradation diminishes soil’s capacity to provide ESs, and support ecosystem functions.
Desertification refers to land degradation in dry/arid regions, which cover approximately 41 % of the continental area . It is the diminution or destruction of the biological potential of land, and can lead ultimately to desert-like conditions . Thus, desertification is a sub-set of land degradation and specifically refers to decline in quality and functionality of soil, vegetation, water, biota, and climate in dry regions. Soil erosion is one of the processes of desertification. Others include salinization, depletion of plant nutrients and soil organic carbon (SOC) pool, reduction in plant available water capacity (AWC) and the overall decline in net primary production (NPP), and denudation of the vegetation cover.
Soil erosion implies physical removal of the soil by tillage, wind, gravity, raindrop splash, surface run-off, stream flow, coastal processes, and chemical dissolution. In the more common forms of water (inter-rill and rill) and wind erosion, the processes comprise of four distinct but inter-related phases: detachment, transport, redistribution, and deposition. The impacts of erosion on soil quality, and ecosystem functions and services depend on the rate (Mg/ha/year, mm/year) of soil erosion vis-a-vis the rate of soil renewal (mm/century or millennia). The accelerated soil erosion, when the rate of soil removal exceeds that of its renewal, has adverse on- and off-site effects. The on-site adverse effects of severe erosion are due to loss of the effective rooting depth, reduction in plant-AWC, depletion of SOC and plant nutrients, decline in soil structure, and reduction in soil quality. The off-site effects of erosion are caused by run-on and inundation, sedimentation, non-point source pollution, and emission of greenhouse gases (GHGs) into the atmosphere. The agronomic, economic, and environmental effects of accelerated erosion are colossal at regional and global scales.
The objective of this review is to describe processes, causes, and factors of soil degradation by erosion and desertification; describe the importance of climate change on these processes; and outline principles and practices of sustainable management of soil and other natural resources.
Climate Change and World Soils
Climate Change and Soil Degradation and Desertification
Estimates of land area affected by land degradation (Modified and adapted from Bai et al. )
Area affected (106 km2)
Percent of the land area
Total NPP Loss (Tg C/y)
Percent of total population affected
Total population affected (billion)
Land area (106 ha)
Potential soil erosion rate (Mg/ha/year)
North America and Central America
The confounding effect of land use conversion on climate change and desertification/erosion because of feedback, thresholds, and non-linearity cannot be ignored. Feedbacks and threshold amplify the risks causing degradation to increase disproportionally faster than population-induced land-use conversion . Among several reasons of the disproportional increase are: (i) reduction in sink capacity of the degraded land to absorb pollutants including CO2, (ii) decrease in soil resilience because of decline in soil quality and functions, (iii) widening gap between demand and supply of water, (iv) increase in environmental injustice arising from inequitable distribution of impacts and resources across social, gender, ethnic, cultural, and income divides, and (v) increase in civil conflict and political unrest. The increasing tide of environmental refugees from desertified land  prone to civil conflict  may also aggravate the adverse impact of the income divides. Decrease in per capita availability of fresh water resources may aggravate the civil conflict , and further increase soil degradation because of societal collapse . Over and above the human dimensions, risks of erosion and desertification are also aggravated by uncontrolled fire and overgrazing [1, 94].
Drought and Desertification
Ragab and Prudhomme  reported that by the 2050s, the West Asia North Africa (WANA) region may have 20–25 % less rainfall during the dry season than the present mean values. With the projected rise in temperature of between 2 and 2.75 °C, the aridization may enhance the risks of drought  and accelerated erosion by wind during the dry season. During the winter time, the rainfall for the same region may decrease by 10–15 % in the south and by 5–10 % in the north, with an average annual decrease of ~10 % . In the Thar desert (India, Pakistan, Afghanistan), average increase in temperature ranges from 1.75 to 2.5 °C and decrease in rainfall by 5–25 %, with relatively more decrease in rainfall during the summer (25 %) than in the winter. Similar trends of increase in temperature have been projected for the Aral Sea basin in Central Asia, and for Australia. Whereas the rainfall may increase in Central Asia (10–25 %), it will decrease in Australia by 20–25 % in the south and 5–10 % in the north. Similar to the WANA regions, risks of drought and desertification will also increase in semi-arid and arid regions of Australia and South and Central Asia. The adverse effects, mostly in the tropics may include the following : (i) decrease in the growing season duration, and (ii) increase in incidence of drought because of uncertainties of the monsoon. The agronomic drought may also be accentuated because of decrease in soil water storage caused by high losses (due to evaporation and run-off), reduction in SOC concentration and structural aggregation. The climate-induced intensification of the hydrologic cycle  lead to acceleration in evaporation, evapotranspiration, and run-off, and intensity of drought. Recent projected temperature increases in the twenty-first century are within the ranges of tipping points or critical thresholds with severe environmental consequences [54, 73]. The effects of tropical deforestation on reduction in precipitation and increase in temperature in the region (Amazon) have been widely established [53, 89]. Additional studies show that the deforestation of Amazon (also Sumatra, Central and West Africa) may significantly affect precipitation elsewhere especially at mid and high latitudes. Avissar and Werth  indicated interesting correlations between the hydrometeorology and the deforested regions and that of remote areas: (i) deforestation of Amazon and Central Africa severely reducing precipitation in lower U.S. Midwest during the spring and summer seasons and in upper U.S. Midwest during the winter and spring when water is crucial for crop growth, (ii) deforestation of Southeast Asia affecting precipitation in China and Balkan Peninsula. The combined effect of deforestation globally decreases winter precipitation in California .
Such coupling of hydrological and climatological factors, especially those which exacerbate risks of drought and desertification, necessitate prudential management of precipitation especially in dryland ecosystems . The strategy is to build resilience to drought in desertification prone regions of Sub-Saharan Africa, WANA, Asia, North America, and South America .
Mutually Reinforcing Positive Feedback Between Soil Degradation/Desertification and Climate Change
Drought, Degradation, and Carbon Sequestration
Restoration of degraded soils by increasing length of the fallow period, converting marginal agricultural areas to rangeland, and conversion to a restorative land use have a large technical potential to sequester C in soils of degraded ecosystems [41, 42, 64] albeit at decadal scale . Therefore, it has been optimistically proposed that irrigated afforestation of the Sahara and the Australian outback can end global warming . Such a bold initiative would imply that man can indeed domesticate himself . A fraction of the large technical potential can be realized only if adequate amount of water and nutrients are also available.
Similar to the potential benefits of the CO2 fertilization effect, those from off-setting of anthropogenic emission by C sequestration in soil and the terrestrial biosphere also cannot be harnessed when water is not adequately available. Jackson et al.  reported that establishment of tree plantations would decrease stream flow by 227 mm per year globally, with 13 % of streams drying completely for at least 1 year. Nonetheless, plantation could improve ground water recharge and upwelling but reduce stream flow. It is because of nutrient and water related constraints that some argue regarding the limited potential for terrestrial C sequestration [26, 86], with perils and potential of this strategy . However, there are numerous co-benefits of soil restoration, C sequestration and of strengthening the ecosystem resilience.
Technological Options for Sustainable Management
Protection of soils and natural resources is critical to maintaining ecosystem services (ESs) essential for human well-being and other functions . Successful adaptation to climate change implies strong understanding of processes and properties of soils and the related natural resources, but also the response of the community. Engaging the natural resource management community  is important to promoting adoption of recommended management practices (RMPs), strengthening science/public dialogue, and enhancing the awareness. Despite availability of a large amount of scientific data toward sustainable management of soils and natural resources since 1950s, about 1.4 billion resource-poor farmers located in risk-prone regions remain untouched by modern agricultural innovations. It is surmised by some that application of the principles of agroecology can provide the needed scientific basis to development and adoption of new management systems fine-tuned to highly variable and diverse farming conditions.
The strategy is to replace what is removed; wisely restore what is altered, and predict and manage what can happen to soil (and natural) resources by anthropogenic and natural perturbations. The ecosystem and soil C pools are critical attributes which affect soil quality and soil/ecosystem resilience. Thus, an important strategy is to enhance the soil and ecosystem C pool by strengthening recycling mechanisms, minimizing losses, and creating positive C and nutrient (N, P, K, S, and Zn) budgets. A brief analyses of the RMPs for sustainable development of agriculture and of natural resources are briefly discussed here.
Soil Carbon and Nutrient Management
Major RMPs include those involving soil and water conservation, conversion from plow till to no-till (NT) farming in conjunction with crop residue mulch and complex crop rotations grown with integrated nutrient management (INM), and use of biomass-C (i.e., manure, compost, mulch, and cover crop) needed to create a positive C budget [41, 42, 43, 44] While the benefits of NT farming are widely known for upland production systems, the techniques is also being recommended and fine-tuned for rice-based systems . The rice–wheat system, practiced on some 14 Mha of cropland in South Asia, provides the staple food grains to 8 % of the world population. In South Asia, (Pakistan, India, Nepal, Bangladesh, Bhutan), the decline or stagnation of the productivity of rice–wheat system since 1990s may be attributed to soil degradation, severe depletion of the SOC reserves, and nutrient imbalance/depletion. Therefore, conversion to mulch farming and NT for wheat, along with direct seeding of aerobic rice in an unpuddled soil in conjunction with a judicious combination of INM strategies and adequate weed control, can reverse the degradation trend, improve soil quality and enhance, and sustain agronomic productivity [45, 50]. Furthermore, present farm yields are low and hardly 40–60 % of the attainable yield potential  and even lower (20 %) in degraded soils and marginal ecosystems. Such a large yield gap can be narrowed by adoption of INM strategies, which are also useful to enhance the SOC pool of degraded and depleted soils [41, 42, 43, 44]. There is a widespread problem of nutrient imbalance, caused by an excessive use of highly subsidized N but not of expensive P, and deficiency of micronutrients (Zn, Fe, etc.). A judicious combination of inorganic fertilizers and organic amendments (compost, manure, and sludge) can alleviate this problem.
Similar to eroded and physically degraded soils, there is a large soil/ecosystem C sink capacity of chemically degraded soils. Important among these are salinized soils in arid and semi-arid ecosystems. In addition to enhancing agronomic productivity, reclamation of salt affected soils also has a high soil C sink capacity to off-set anthropogenic emissions .
There is a close link between C, N (P, S), and water, and understanding and managing this link is important to improving soil quality and resilience. Water deficit, already a serious problem even in humid regions because of poor distribution, is likely to be exacerbated by the changing and uncertain climate with increase in frequency of extreme events. The drastic situations of water deficit in harsh environments of Middle Eastern regions  have led to some drastic measures such as changing texture of sandy soils by mixing clay to enhance water retention . Sustainable waste water management, especially for small communities, in Middle East and elsewhere in arid and semi-arid regions, can be useful to improve agronomic production .
Another strategy is to explore the nexus between integrated natural resource management (NRM) and integrated water resource management  because of the co-cycling within an ecosystem/watershed. The strategy is to redirect blue water issues to green water issues and vice versa [22, 23]. Indeed, sound water management requires a better understanding of the opportunity cost of water and greater coordination of sectoral strategies, especially among agriculture, industry, and urban uses .
In the final analyses, the significance of the judicious NRM within a watershed (especially in semi-arid and arid regions) cannot be over emphasized. Indeed, the integrated use of soil and water conservation practices with balanced plant nutrition is an important basis of enhancing the water productivity and resource use efficiency . The goal is to effectively manage the precipitation  to obtain more crops per drop of water.
Then, there is also an important issue of wetland and their management, because wetland ecosystems are a natural resource of global significance . Wetlands, as kidneys of the ecosystem, provide protection against floods and non-point sources pollution, and are also a major source of fresh water. Wetlands have numerous ESs (e.g., biodiversity, C sequestration, water purification and decontamination, aquaculture, and wetland restoration) and can enhance these ESs, especially the C sink capacity to off-set anthropogenic emissions . In this regards, it is important to realize that wetlands are prone to drainage and degradation especially in arid regions. Eutrophication is a major threat to hydrophytic and other hydric species , and policy interventions are needed to protect and restore these valuable resources.
A judicious management of the humid tropical forests (spanning ~5° N and S of the equator) is important to numerous ESs of global significance. Given the significance to global C and water cycles and conservation of biodiversity, tropical forest resources must be protected and restored. Forest management, and integration of trees with crops and livestock through appropriate agroforestry systems, can also conserve and improve soil and ecosystem C pools. Phat et al.  reported that between 1990 and 2000 in Southeast Asia, about 2.3 Mha of forest were cleared every year and emitted 46.5 Tg of C into the atmosphere (~29 % of the global net C release by deforestation). Thus, there is a strong need to develop policy for reforestation and afforestation of the previously deforested land. Scatena  advocated the use of ecological rhythms in the management of endangered species and water resources in the Caribbean. Such a dynamic management is a challenging task. However, integrating ecological rhythms into management options is an important strategy for both tropical and temperate environments. Similarly, a judicious management of plantation forests is an opportunity and a challenge. Implications for biodiversity of the intensively managed plantations are a major issue. Although natural forests are a better habitat for biodiversity, judicious management of plantation forests can provide a valuable habitat , while also creating other ESs. During the early stages of tree development, agroforestry techniques can be adapted to enhance productivity and biodiversity .
Similar to the rainforest biome, tropical grasslands and savannas occupy approximately 210 Mha in South America . Reconciling intensified grazing systems with NT farming and INM have a large soil/ecosystem C sink capacity .
New Research and Analytical Tools
Strong scientific understanding is the basis for identifying technological options to be implemented for sustainable NRM. The knowledge base improvement requires credible data from long-term hypothesis based research to establish the cause-effect relationship . In addition, innovative experimental techniques can improve the data procurement, analyses and synthesis. Remote sensing and the geographic information system (GIS) are useful tools to assess ecosystem characteristics and functions . These techniques can be used to study the change in land-use/cover and soil degradation in diverse ecoregions. There are also several modeling techniques to study biophysical processes, and also assess the anthropogenic interactions or the human dimensions of ecosystems. Nautiyal and Kaechele  used modeling approach to understanding how human behavior is changing under shifting political, socioeconomic, and environmental conditions in the Indian Himalayas. There are also decision support system (DSS) for soils and water conservation within a watershed. Saragni et al.  used DSS for generating alternative decision support scenarios to facilitate integrated watershed management concepts in an interactive and holistic manner.
Sustainable management must also be linked to sustainable governance of natural resources. Sustainable governance is essential to place the politically neutralizing discourse of management in the context of a wider social debate to discuss and negotiate the norms, rules, etc., of NRM and sustainable development . Thus, there is a need for the judicious governance of natural resources. The goal is to move from strategic action to communicative action .
There is a philosophical emphasis on the strategy of community-based natural resource management (CBNRM). The latter involves the governance of economic processes, property right, and local political organizations . It implies replacement of fiscal centralization, fees and bureaucracy which have undervalued natural resources to provide comparative economic advantage to small land holders with community incentives. The resource governance should be shifted to the community, thus benefits can be shared at the local level. To be successful, CBNRM strategy must be accountable, transparent, and based on equitable governance at micro- and meso-level .
There exists a close link between soil erosion/degradation, climate change, and poverty. Soil degradation creates a positive feedback attributed to emission of radiatively active gases depletion of soil organic carbon and nutrient pools, denudation of vegetation cover, and reduction in net primary productivity, increase in frequency and intensity of droughts (especially pedological and ecological droughts), and loss of ecosystem resilience. There is a strong need for prudent management of soil, vegetation, water, and other natural resources. Restoration of degraded soils can increase the ecosystem C pool provided that available water and plant nutrients are adequate. Establishment of tree plantations can reduce stream flow while also decreasing albedo. The strong link between the climate–vegetation–soil–water–continuum and anthropogenic activities necessitate a prudent and a coordinated effort to reverse the downward spiral, restore degraded soils, mitigate climate change, and enhance ecosystem services. There are new tools and techniques available to measure, monitor and verify the status of soils, and natural resources. The community-based natural resources management is a useful strategy for judicious governance. The strategy is to shift from strategic action to strategic governance.
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