Climate Change and Global Food Security - Section 6 (end) pdf

733 30.1.1.1 Climate Change: CO2 Fertilization Impacts on Terrestrial Ecosystem Production..... But most would concur that several impacts will result, namely: • A rise in the mean globa

Section VI

Toward Research and Development Priorities

30

Researchable Issues and Development Priorities for Countering Climate Change

RATTAN LAL, B.A STEWART, DAVID O HANSEN, AND NORMAN UPHOFF

CONTENTS

30.1 Issues 732 30.1.1 Climate Change and Net Primary

Production 733 30.1.1.1 Climate Change: CO2 Fertilization

Impacts on Terrestrial Ecosystem Production 733 30.1.1.2 Climate Change Impacts on

Forest Ecosystems 733 30.1.1.3 Climate Change Impacts on

Water Supply 734 30.1.2 Global Warming and Food Insecurity 734

30.1.2.1 Greenhouse Gases and Food

Security in Low-Income Countries 734

30.1.2.2 Effect of Global Climate Change

on Agricultural Pests 734 30.1.2.3 Impact of Climate Change on

Agricultural Production in Different Regions 735 30.1.2.4 Modeling Future Climate

Changes and Crop Production Scenario Challenges 735 30.1.2.5 Policy Considerations Related to

Twin Problems of Global Warming and Food Insecurity 736 30.1.3 Terrestrial Carbon Sequestration and

Food Security 736 30.1.3.1 Environmental and Socioeconomic

Context for Soil Carbon Sequestration 737 30.1.3.2 Land Use, Soil Management, and

Soil Carbon Sequestration 737 30.1.3.3 Modeling and Extrapolating Soil

Carbon Sequestration 738 30.1.3.4 Environmental and Socioeconomic

Analysis of Soil Carbon Sequestration 738 30.1.4 Policy and Economic Issues 739

30.1.4.1 Policies and Incentives for

Permanent Adoption of Agricultural Carbon Sequestration Practices in Industrialized and Developing Countries 739 30.1.4.2 Climate Change, Poverty, and

Resource-Friendly Agriculture 740 30.1.4.3 Climate Change and Public

Policy Challenges 741 30.1.4.4 Climate Change Impacts on

Developing Countries 741 30.1.4.5 Climate Change and Tropical

Agriculture: Implications for Social Vulnerability and Food Security 742

30.2 Identification of Researchable Priorities 742 Acknowledgments 744 References 744

The globe has experienced a 31% increase in the atmospheric concentration of carbon dioxide (CO2) and substantial increases in other greenhouse gases (GHGs) since the indus-trial revolution (Intergovernmental Panel on Climate Change [IPCC], 2001) The current rate of increase of CO2 is about 0.5% or 1.5 ppm per annum At this rate, the concentration

of atmospheric CO2 will double by the end of the 21st century Environmental and related agricultural impacts of this increased concentration of CO2 and other GHGs are subject

to debate But most would concur that several impacts will result, namely:

• A rise in the mean global temperature, which will cause alterations in the amount and distribution of precipitation, and local, regional, and global changes

in water and energy balances

• A fertilization effect of increased atmospheric CO2 on plant growth, with probable increases in biological productivity and water-use efficiency

• A decrease in soil organic carbon (SOC) pools, accom-panied by a decline in soil quality and an increase in soil erosion and other degradation processes

• An increase in the incidence of pests and pathogens with attendant adverse effects on crop yields and food production

• Adverse effects on global food security, especially in tropical and subtropical regions that are character-ized by soils prone to degradation, large numbers

of resource-poor farmers, and high demographic pressures

Climate shifts have occurred almost constantly during the Earth’s history However, the rate of projected change during the 21st century may be unprecedented Interacting factors involved in this process are complex However, it is

important to assess whether global agricultural production will increase or decrease, whether the quality of soil and water resources will improve or decline, whether the beneficial effects of CO2 fertilization will be enhanced or nullified by other adverse impacts of global warming such as decline in soil quality, and whether food security will be jeopardized in regions with fragile soils and high population density

Anthropogenic activities, especially land use change and conversion of natural to agricultural ecosystems, have con-tributed to enrichment of GHGs in the atmosphere since the dawn of civilization (Ruddiman, 2003) Land use conversion and agricultural activities also adversely impacted soil qual-ity Further, the atmospheric concentration of GHGs is also closely related to soil quality A decline in soil quality, which results from accelerated erosion and the reduced soil fertility associated with subsistence farming, contributes to the release of CO2 and other GHGs into the atmosphere Since

1850, global terrestrial ecosystems have released 136 ± 55 Pg (billion metric tons) of C, while fossil fuel emissions have contributed 270 ± 30 Pg (IPCC, 2000) Regarding emissions from terrestrial ecosystems, reductions in the SOC pool rep-resent 78 ± 12 Pg (Lal, 1999) The conversion of natural eco-systems to agricultural ecoeco-systems may have depleted as much as 30% to 50% of the SOC pools in the soils of temperate regions and 50% to 75% of those in the tropics (Paul et al., 1997; Lal, 1999, 2000) Depletion of the SOC pool is exacer-bated by erosion and soil degradation Degraded soils in Sub-Saharan Africa and elsewhere in developing countries have low SOC pools because of nutrient mining and accelerated erosion Enhancement of SOC pools through soil restoration would reverse degradation trends, improve soil quality, increase agronomic/biomass productivity, and mitigate cli-mate change

30.1 ISSUES

Several major issues related to projected climate changes need to be given greater attention in national and interna-tional fora These issues are summarized below

30.1.1 Climate Change and Net Primary

Production

Three globally significant issues are as follows:

30.1.1.1 Climate Change: CO2 Fertilization

Impacts on Terrestrial Ecosystem

Production

The relative contributions of CO2 fertilization and climate change effects on terrestrial CO2 sources and sinks have been estimated for different ecoregions They suggest that the CO2 effect on total net primary production (NPP) content will be positive, and that NPP will decrease without it On the other hand, the effect of projected climate changes on total NPP appear to be negative Aggregate global impacts

of CO2 fertilization and climate change on CO2 appear to

be positive

Modeling results also suggest that the geographic dis-tribution of NPP will change along with changes in CO2 and climate Ecosystems with the highest NPP show the great-est change The effects of other factors, such as land use history and nitrogen cycling, have generally not been con-sidered in these simulation models They need to be care-fully assessed

30.1.1.2 Climate Change Impacts on Forest

Ecosystems

Free-air CO2 enrichment (FACE) experiments have shown that trees grow faster under elevated levels of CO2 These findings suggest that temperate forests may be stimulated by higher atmospheric CO2 levels However, data also suggest that tree growth may be negatively affected by increasing temperatures In warmer climates, tropical forests could become a source rather than a sink for CO2 If all forests in the world were to experience stimulated growth from increased atmospheric CO2 levels, the effect would be minor relative to CO2 emissions from continued fossil fuel burning

30.1.1.3 Climate Change Impacts on Water

Supply

The potential impacts of climate change on global water sup-plies are of great importance Results of a general circulation model (GCM) based on watershed data suggest that water flows will increase during the fall, winter, and spring seasons, but decrease during the summer However, the increased demand for water associated with projected population increases will offset any additional water supplies over time Future climate changes may reduce the carrying capacity of major reservoirs and water flows in rivers around the world because of large water demands for irrigated agriculture

30.1.2 Global Warming and Food Insecurity

Projected climate changes may adversely affect global and regional food security

30.1.2.1 Greenhouse Gases and Food Security

in Low-Income Countries

Climate change may impact food security in different ways Some parts of the world — notably West Africa — have already been adversely impacted by climate change Signifi-cant differences in regional food gaps may be explained at least in part by higher levels of agricultural productivity in Latin America and Asia as compared to Sub-Saharan Africa

A major challenge facing food-deficit regions is to address long-term issues, such as global climate change, while also dealing with shorter-term issues such as availability of fertil-izers, farm machinery, land tenure, and so on

30.1.2.2 Effect of Global Climate Change on

Agricultural Pests

The manner in which climate change will impact the incidence

of pests and diseases is a potentially important but under-studied problem Pest incidences may shift in response to climate change The “standard model,” based on temperature

and precipitation, may be useful for studying impacts of cli-mate change, but much more research needs to be done Most crop models that are used to predict impacts of climate change

on production fail to incorporate pests The problem is com-pounded by the complexity of the climate processes Nitrogen appears to have important effects on insect herbivores and

on important species interactions that are not well under-stood It is also important to disconnect the scale at which tests are impacted by climate change from the scale used for GCM models Pest–climate interactions with climate change need to be assessed

30.1.2.3 Impact of Climate Change on

Agricultural Production in Different

Regions

Projected climate changes could affect crop yields and soil carbon in different regions of the world In fact, severe adverse impacts in the tropics could occur Modeling studies based on data from Brazil show that changes in temperature and rain-fall may result in soybean production increases and maize and wheat production decreases by 2050 In a case study of the Amazon Basin in which forested areas were converted to pastureland, the soil carbon pool was projected to decrease

by 30% over a 100-year period A decline in the SOC pool would have adverse impacts on soil quality and result in a decline in agronomic productivity and the capacity of the environment to moderate changes

30.1.2.4 Modeling Future Climate Changes and

Crop Production Scenario Challenges

The prediction of impacts of climate change on agricultural research and the use of crop models to assess the potential impacts of climate change suffer from several limitations Crop models can result in accurate predictions when they are based on observed data, but are much less reliable when based

on data that are downscaled from GCMs A key limitation of GCM data appears to be an inability to represent extreme

weather events, particularly those associated with precipita-tion The hydrological cycle in the U.S Midwest is not well represented by downscaled GCM data, because of nonlinear and feedback effects in more detailed regional climate models

30.1.2.5 Policy Considerations Related to Twin

Problems of Global Warming and Food

Insecurity

There are major policy issues related to aspects of climate change The world faces important food insecurity and global warming challenges in the 21st century Previous research failed to suggest that global warming will have a large impact

on aggregate food availability However, it does suggest that global warming could have some major regional effects on food security, especially in the tropics, in which 800 million people are already at risk The solution to the food security problem

is to address the more fundamental problem of poverty The

“standard model,” based on the “Washington consensus,” may

be the best starting point for economic development This model emphasizes markets and institutions in infrastructure, education, and agricultural research This model is not always used for political and cultural reasons Nevertheless, past efforts indicate that an important step in promoting national food security is to develop economies to the point at which nations can afford to address environmental sustainability as well as economic growth

30.1.3 Terrestrial Carbon Sequestration and

Food Security

Carbon sequestration in soil and vegetation, as well as tem-poral and spatial variations in relation to land use and man-agement and their related policy issues have major implications for global food security, climate change, and envi-ronmental quality

30.1.3.1 Environmental and Socioeconomic

Context for Soil Carbon Sequestration

Land degradation is a constant major threat to food security, especially in Africa and Asia Soil carbon sequestration (SCS) can be a major way to counter increases in atmospheric CO2 and to reduce land degradation The conservation of tropical forests and reforestation activities can offset fossil fuel use

In fact, drastic reductions in rates of deforestation are needed

to protect the positive functions of tropical ecosystems A serious problem of land degradation exists in the humid trop-ics, and there is an urgent need to find alternatives to slash-and-burn agriculture in this region Similarly, SCS in coun-tries in the Sahel region may be an important way to increase carbon sinks, control desertification, and promote sustainable agriculture and improved livelihoods for its small farmers Degraded lands have low soil C content SOC concentration

in degraded topsoils of Africa varies from 5 to 20 MT ha−1 An urgent need exists to implement SCS practices in order to improve soil quality and farmer livelihoods while removing CO2 from the atmosphere

30.1.3.2 Land Use, Soil Management, and Soil

Carbon Sequestration

There are several examples of SOC sequestration from exper-iments that combine SCS practices with alternative food pro-duction systems The rate of aboveground C sequestration ranges from 1 to 5 MT C ha−1 year−1 in the tropics, but C stocks associated with the traditional peanut-based cropping system

in Sub-Saharan Africa ranged from 5 to 25 MT C ha−1 The clay content in soils has a strong effect on C stocks

Overall rates of SCS in the tropics are lower than those found in higher latitudes (Lal, 2002) Most C accrual is accounted for by a limited number of plant species in agro-forestry systems that use fruit and palm trees, timber–pas-ture combinations, and secondary-growth forest Soil C accrual rates are difficult to estimate due to the presence of charcoal in fire-prone or fire-dependent ecosystems, such as