Balancing Food Security and Climate Change Mitigation for Sustainable Land Use in the Tropics

Two of today’s major problems are the need to increase food production to achieve food security, and the need to mitigate climate change.  However, their potential solutions produce a conflict.  DeFries and Rosenzweig (2010) look at the trade-offs that the solutions entail in tropical regions, and note that tropical countries highly value both the agriculture<!–[if supportFields]>XE “agriculture” <![endif]–><!–[if supportFields]><![endif]–> and forest<!–[if supportFields]> XE “forest” <![endif]–><!–[if supportFields]><![endif]–> sectors, but the extensive land use in these areas tends to exacerbate climate change. On the other hand, global food production is only slightly increased by deforestation<!–[if supportFields]> XE “deforestation” <![endif]–><!–[if supportFields]><![endif]–>-related agricultural development.  Redirection of agricultural expansion to already cleared lands, improvement of soil quality and livestock management, and other policy intervention may allow increased agricultural production without exacerbating climate change.  The authors find that there is no easy balance for achieving these objectives in the tropics, but place-specific strategies based on regionally varying factors are a start. —Whitney Dawson
DeFries, R., Rosenzweig, C., 2010.  Toward a whole-landscape approach for sustainable land use in the tropics.  PNAS published ahead of print November 16, 2010, doi:10.1073/pnas.1011163107

DeFries and Rosenzweig use past studies to examine the linkages between climate change mitigation and food security. They find that the greatest possibility to mitigate climate change is through change in agricultural land use.  The only remaining biomes where enough land is available for expansion of agricultural production are in tropical forests and woodlands.  However, agricultural expansion is the primary cause of deforestation<!–[if supportFields]> XE “deforestation” <![endif]–><!–[if supportFields]><![endif]–>. Estimates from various data sources strongly conclude that deforestation results in a very small increase of agricultural area, but causes a huge increase in carbon dioxide emissions. The majority of greenhouse gas emissions in tropical countries are due to the use of land for agricultural practices, different from most other countries whose mitigation possibilities are in the energy sector.  The predominant agricultural activity that emits GHGs is controlled fires for clearing biomass for deforestation.  Tropical regions are increasing GHG emissions at the most rapid rate.
Agricultural intensification, or increasing output per area, is identified as a primary focus for increasing food production in a more sustainable manner.  Intensification would allow less deforestation<!–[if supportFields]> XE “deforestation” <![endif]–><!–[if supportFields]><![endif]–> to occur due to a more efficient use of land, and would therefore result in less GHG emissions.  A possible exception the authors point out is that higher livestock densities and chemical inputs might result from intensification, which would both add to the level of emissions. Based on multiple analyses, the authors concluded that reducing deforestation will not necessarily lead to increased food production.
DeFries and Rosenzweig suggest the need to view landscapes from a cross-sector perspective to recognize opportunities that minimize trade-offs between food production and climate change mitigation.  The authors emphasize the need to examine agricultural practices at a local level, since specific areas have a wide array of variables that also affect crop yields.   Strategies to achieve the objectives require analyses of options that consider site-specific characteristics.  Trade-offs between food production and climate change mitigation vary between small and large-scale agricultural systems. 
The foremost opportunity for tropical countries to mitigate climate change arises in the forest<!–[if supportFields]> XE “forest” <![endif]–><!–[if supportFields]><![endif]–> and agricultural sectors.  Emissions of GHGs are increasing at a more rapid rate in tropical Asia and Latin America than in the rest of the world.  Compared to temperate regions, almost twice as much carbon is lost from a unit of cleared land in the tropics, producing less than half of the crop yield.  The opportunities for mitigating climate change and increasing agricultural production will not spontaneously occur, but will require the help of policies.  Policy options discussed have been heavily focused on the mitigation potential of REDD (Reducing Emissions from Deforestation and forest Degradation), although this option does not consider food security.  A careful balance must be made when considering policies that deal with deforestation<!–[if supportFields]> XE “deforestation” <![endif]–><!–[if supportFields]><![endif]–> because food production could be negatively affected.  DeFries and Rosenzweig note that policies should aim at locating new production opportunities on land that has already been cleared, rather than clearing new land.   They suggest a policy focus on guidelines for international trade that encourage agricultural commodities produced on already cleared land. 

Examining the Impact of Thermal Adaptation of Soil Microorganisms and Crop System on Climate Change’s Effects on Organic Matter in Tropical Soil

As populations in tropical regions increase and more food is needed, crop yields are decreasing. Increasing the amount of cleared land for crop production has negative impacts on soil quality and crop production as well as increasing the amount of greenhouse gas emissions.  Tropical crops are currently at optimal growth temperatures, and therefore decline in yields are expected with even a small increase in temperature.  Sierra et al. (2010) hypothesize that climate change in tropics affects soil organic matter<!–[if supportFields]> XE “soil organic matter (SOM)” <![endif]–><!–[if supportFields]><![endif]–> (SOM) content and soil fertility through the direct effect on the rate of microbial processes and by the indirect effect on crop growth.  The authors predict that temperature and rainfall will substantially increase, and affect maize<!–[if supportFields]> XE “maize” <![endif]–><!–[if supportFields]><![endif]–> crops significantly more than bananas.  Maize yields were found to decrease by 1% under the adaptation scenario studied, where no difference was found in banana yields. Decreasing rates of SOM and C mineralization were predicted for maize, and again no differences were found for banana crops. —Whitney Dawson
Sierra, J., Brisson, N<!–[if supportFields]>XE “nitrogen, N”<![endif]–><!–[if supportFields]><![endif]–><!–[if supportFields]> XE “nitrogen” <![endif]–><!–[if supportFields]><![endif]–>., Ripoche, D., Deque, M., 2010. Modelling the impact of thermal adaptation of soil microorganisms and crop system on the dynamics of organic matter in a tropical soil under a climate change scenario.  El Selvier 221, 2850–2858.ces 2, 29–35.

Sierra et al. model the thermal adaptation, the shift in the intrinsic response of a biological soil process to temperature due to soil warming, of soil microorganisms in response to climate change.  This process is then introduced in a crop system model, already calibrated to incorporate SOM<!–[if supportFields]> XE “soil organic matter (SOM)” <![endif]–><!–[if supportFields]><![endif]–> dynamics under tropical conditions. The study aims to see how climate change impacts SOM in agricultural tropical soil, and to evaluate the importance of microbial adaptation in SOM dynamics in crops.  The two crop systems compared are maize<!–[if supportFields]> XE “maize” <![endif]–><!–[if supportFields]><![endif]–> and banana, both currently of great use in the tropics.   Models for climate simulation and crop-soil relationships were borrowed from outside sources, selected for their previous calibration to the crops analyzed in this study, and accounting for irrigation effects.  The climate is simulated from 1950 to 2099 for tropical humid conditions.
The model predicts a 3.4 °C increase for air temperature and 1100 mm per year increase for rainfall due to an increase in of 375 ppm for atmospheric carbon dioxide concentration in the 2090–2099 decade in comparison to the 1950–1959 decade.   By controlling the change in C input, soil temperature, and soil moisture, the crops affects the response of SOM<!–[if supportFields]> XE “soil organic matter (SOM)” <![endif]–><!–[if supportFields]><![endif]–> to climate change. Little variation is seen in SOM until 2020, followed by a faster decrease for maize<!–[if supportFields]> XE “maize” <![endif]–><!–[if supportFields]><![endif]–> than banana. Banana had positive effects on growth from an increase in temperature, and relatively stable C inputs.  Maize growth and cycle length drastically decreased from increased temperature.  The difference in results between crops is due to the higher water consumption of banana than maize, affecting the soil temperature as well.  SOM is never stabilized in the period studied since C mineralization is always greater than C input.  The authors conclude from the models that microbial thermal adaptation does not fundamentally change the temporal pattern of SOM dynamics, but slightly modifies it.
Debate over climate change impacts occurs as a result of the difficulties is examining the relationship between soil, plant, and weather variables affecting SOM<!–[if supportFields]> XE “soil organic matter (SOM)” <![endif]–><!–[if supportFields]><![endif]–> dynamics under the scenario of climate change.  In the studied period, the factors controlling SOM decrease varied over time and with the crop system, not with a large amount of consistency.  It is suggested that progressive thermal adaptation of soil microorganisms can play an important role in mitigating climate change. 

Climate Change Mitigation Possibili-ties through Carbon Sequestration in the U.S.

The United States is an active player in the international effort to combat climate change.  Although 84% of US net carbon emissions come from fossil fuel consumption and only 7% from agriculture<!–[if supportFields]> XE “agriculture” <![endif]–><!–[if supportFields]><![endif]–>, the changes made in the agricultural system to fight climate change are still essential until new technologies and strategies become prevalent.  Agriculture is both largely affected by climate change, as well as a large contributor itself to the growing problem.  The management of agricultural systems to sequester carbon dioxide as soil organic carbon<!–[if supportFields]> XE “soil organic carbon (SOC)” <![endif]–><!–[if supportFields]><![endif]–> (SOC<!–[if supportFields]> XE “soil organic C, SOC” <![endif]–><!–[if supportFields]><![endif]–>) and to minimize GHG emissions is a partial solution for climate change mitigation.  Morgan et al. examine the various agricultural sectors in the United States for their SOC potential, distinguishing the different land characteristics. —Whitney Dawson
 Morgan, J.A., Follett, R., Hartwell Allen, L., Del Grosso, S., Derner, J., Dijkstra, F., Franzlubbers, A., Fry, R., Paustian, K., Schoeneberger, M., 2010.  Carbon sequestration<!–[if supportFields]>XE “sequestration” <![endif]–><!–[if supportFields]><![endif]–> in agricultural lands of the United States.  Journal of Soil and Water Conservation 65, 6A–13A.

Morgan et al. (2010) explain that the rate of carbon return to the atmosphere is influenced by the rate of photosynthetic carbon dioxide assimilation, which is dependent on soil fertility, climate, and management.  Greenhouse gas mitigation is possible through assimilation of atmospheric carbon dioxide by vegetation<!–[if supportFields]> XE “vegetation” <![endif]–><!–[if supportFields]><![endif]–> choices, and moving carbon from plants and animals into soil.  Sequestering carbon within the soil organic matter<!–[if supportFields]>XE “soil organic matter (SOM)”<![endif]–><!–[if supportFields]><![endif]–> (SOM) is a prime option for carbon storage but has other benefits as well, such as improved soil quality, soil structure and stability, and water holding capacity.
The authors study each agricultural sector, picking apart possible improvements, and recognize valuable questions to be answered.  To increase SOC<!–[if supportFields]> XE “soil organic carbon (SOC)” <![endif]–><!–[if supportFields]><![endif]–><!–[if supportFields]> XE “soil organic C, SOC”<![endif]–><!–[if supportFields]><![endif]–> in croplands, the authors recommend increasing cropping frequency, growing high-residue crops, maximizing plant water use, and applying vegetation<!–[if supportFields]>XE “vegetation”<![endif]–><!–[if supportFields]><![endif]–> to shade the surface soil.  Grazing lands take up about 37% of total US land area and contribute about 15% of US soil carbon sequestration<!–[if supportFields]> XE “carbon sequestration” <![endif]–><!–[if supportFields]><![endif]–> potential.  The amount of carbon stored in grazing<!–[if supportFields]> XE “grazing” <![endif]–><!–[if supportFields]><![endif]–> lands can be double that of cropland and can be intensified by adjusting stocking rate, plant species, and fertilizer<!–[if supportFields]> XE “fertilizer” <![endif]–><!–[if supportFields]><![endif]–> use. Sequestration rates decline in grazing lands over time without added inputs, therefore attention to these areas is key.  Agro forestry is the integration of woody plants into crop and livestock systems for improvement of the quality of their environment, while still allowing sustainable production of food.  This system sequesters a large amount of carbon and for a long duration.  Horticulture land has received little attention for the potential of carbon sequestration<!–[if supportFields]>XE “sequestration” <![endif]–><!–[if supportFields]><![endif]–> in its vegetable, vineyard, and orchard crops.  Specialized management of the crops has discouraged the use of much conservation potential but the authors suggest cover crops for sequestering carbon.  Wetlands are less than 1% of cropped areas in the US, but have especially high GHG emission rates due to their waterlogged state, which lacks the oxygen needed to decompose organic matter.  Drainage of the organic matter would allow carbon dioxide to be released at a higher rate, but the authors conclude that it is not feasible to consider carbon sequestration in these soils.
Biofuels present an emerging issue for land management.  About 18% of harvested grain in the US was used for ethanol<!–[if supportFields]> XE “ethanol” <![endif]–><!–[if supportFields]><![endif]–> production in 2007, and more than half of harvested corn grain was for animal feed.  Strong interest exists in developing sustainable energies from biofuels, but a number of concerns for environmental problems have risen from intensification of agriculture<!–[if supportFields]>XE “agriculture” <![endif]–><!–[if supportFields]><![endif]–> and may compromise the overall goal of increasing carbon in the ecosystem. Even as new technologies are developed, it is important for agriculture to continue developing successful soil carbon sequestration<!–[if supportFields]>XE “carbon sequestration” <![endif]–><!–[if supportFields]><![endif]–> practices. 
Very few experiments have addressed best management practices for improving soil carbon storage, and little research has assessed how different practices may affect carbon sequestration<!–[if supportFields]> XE “carbon sequestration” <![endif]–><!–[if supportFields]><![endif]–>.  Morgan et al. suggest the need for low-cost carbon and non-carbon dioxide greenhouse gas information on multiple levels.  Measurements of GHG fluxes<!–[if supportFields]> XE “flux” <![endif]–><!–[if supportFields]><![endif]–> can be used to evaluate the effects of management opportunities and changes in climate on carbon balance, and could be used to estimate large-scale carbon budgets.  Development of a national database is needed to make further assessments.  The authors recommend direct sampling of soil carbon as a more feasible technique for gathering data, rather than expensive and complicated GHG measurement technology.

Climate Change and South American Farmers’ Livestock Choices

South American farmers choose livestock species for agriculture<!–[if supportFields]>XE “agriculture” <![endif]–><!–[if supportFields]><![endif]–> use based on the range of climate.  They specialize in beef and cattle exports, which are the primary species on around 48% of farms, but climate change will likely have a negative impact on agricultural production, and threaten food security.  Seo et al. (2010) examine how the livestock choices will respond to climate change, looking at five species in seven countries.  The multinominal logit model used in the study proved climate variables are highly significant in determining the species choice.  Large changes were seen in Andean countries, but overall the impacts from climate change vary by species and climate.—Whitney Dawson
Seo N<!–[if supportFields]> XE “nitrogen, N” <![endif]–><!–[if supportFields]><![endif]–><!–[if supportFields]> XE “nitrogen” <![endif]–><!–[if supportFields]><![endif]–>. S., McCarl, B. A., Mendelsohn, R., 2010.  From beef cattle to sheep<!–[if supportFields]> XE “sheep” <![endif]–><!–[if supportFields]><![endif]–> under global warming?  An analysis of adaptation by livestock species choice in South America. El Selvier published ahead of print August 20, 2010, doi: 10.1016/j.ecolecon.2010.07.025

Seo et al. developed a multinominal logit model to measure the effects of climate change on livestock species.  Farmers from a broad array of climate conditions in seven different countries were surveyed to collect data for the model.  The data set includes information on livestock production and transactions, livestock products, and relevant costs.  The five primary livestock species that were examined are commonly raised in South America: beef cattle, dairy cattle, pigs, sheep<!–[if supportFields]> XE “sheep” <![endif]–><!–[if supportFields]><![endif]–>, and chickens.  The model controlled for soils, geography, household characteristics, and country fixed effects.  Climate data for a 16-year time period were gathered from satellites operated by the US Department of Defense, and the ground weather measurement from the World Meteorological Organization. 
The scientific evidence that livestock production is strongly affected by climate conditions is convincing, and seen in impacts to animal performance, the supply of feedstuffs, and disease distribution. A hot and dry scenario showed a decrease in beef cattle by 3.2%, dairy cattle by 2.3%, pigs by 0.5% and chickens by 0.9% by 2060, and an increase in sheep<!–[if supportFields]>XE “sheep” <![endif]–><!–[if supportFields]><![endif]–> by 7% to compensate.  The increase in sheep occurs mostly in Andes<!–[if supportFields]> XE “Andes” <![endif]–><!–[if supportFields]><![endif]–> mountain countries, but decreases in the higher mountain areas, where chickens are more frequently chosen.  A warmer temperature is likely to cause cattle productivity to fall, and to impact reproduction rates. Chickens are opted for in wetter zones, and dairy cattle choice increases with precipitation, but so does the incidence of livestock diseases.
The study was unique in comparison to past similar studies, in that it controlled detailed household level information data in the model.  The data included in the model controlled for multiple variables, and household information was controlled to determine how various farm heads would change their livestock choices.  Older farm heads prefer cattle, and more educated farm heads prefer beef cattle or pigs.  Female farm heads and long time private landowners tend to avoid chickens.  These results demonstrate a female tendency to choose less risky species in comparison to younger male farm heads, in their choosing of beef cattle, a more profitable species.
Where many livestock species choices vary across the countries in South America, the choice of beef cattle will decline across the continent.  Beef cattle are an important part of the agriculture<!–[if supportFields]> XE “agriculture” <![endif]–><!–[if supportFields]><![endif]–> industry across the continent, and the authors suggest concern on a policy level due to its vulnerability, and the high dependency on the agricultural economy.  Although dairy cattle choice will decline across the continent, increases are seen in Uruguay and Argentina<!–[if supportFields]> XE “Argentina” <![endif]–><!–[if supportFields]><![endif]–>. The likelihood of choosing sheep<!–[if supportFields]> XE “sheep” <![endif]–><!–[if supportFields]><![endif]–> increases across all countries.  Climate changes are going to change livestock patterns on a large scale because the entire ecosystem is likely to change.  If the current savannah habitat changes to forest<!–[if supportFields]>XE “forest”<![endif]–><!–[if supportFields]><![endif]–>, livestock grazing<!–[if supportFields]> XE “grazing” <![endif]–><!–[if supportFields]><![endif]–> will become difficult.  Seo et al. found that farmers are more likely to choose livestock over crops as temperature increases, though the livestock species adopted varies greatly.  
The authors did not include price as a variable in their model, and do not know how price will change in the future, nor did they examine potential changes in population, taste, technologies, reliance on regional agriculture<!–[if supportFields]> XE “agriculture” <![endif]–><!–[if supportFields]><![endif]–> economy, and in political structures.  These unaccounted for changes could affect agricultural practices greatly, and farmer revenue changes would also have a large impact on livestock species choice. 

European Agriculture Responses to Climate Change

The productivity of European agriculture<!–[if supportFields]> XE “agriculture” <![endif]–><!–[if supportFields]><![endif]–> is generally higher than the world average.  In 2003 the European Union decided to change the agricultural policy to link farmer payment to respect for the environment, animal and plant health, and animal welfare standards.  The consequences of climate change are expected to cause increasing water shortages and a varying response in cropping systems.  Bindi and Oleson (2010) expect increasing yields and suitable crop areas in northern Europe<!–[if supportFields]> XE “Europe” <![endif]–><!–[if supportFields]><![endif]–>, but expect disadvantages from water shortage and extreme weather in southern Europe.  The authors discuss positive possibilities for different use of the land that will become incapable of crop production due to climate change.—Whitney Dawson
Bindi, M., Oleson, J., 2010.  The reponse of agriculture<!–[if supportFields]> XE “agriculture” <![endif]–><!–[if supportFields]><![endif]–> in Europe<!–[if supportFields]> XE “Europe” <![endif]–><!–[if supportFields]><![endif]–> to climate change. Springer-Verlag published ahead of print November 16, 2010, doi:10.1007/s10113-010-0173-x.

Bindi and Oleson find that the impact of agriculture<!–[if supportFields]> XE “agriculture” <![endif]–><!–[if supportFields]><![endif]–> on Europe<!–[if supportFields]> XE “Europe” <![endif]–><!–[if supportFields]><![endif]–>’s water resources should be reduced to reach higher surface and ground water standards.  The authors also discuss the changes in climate that are expected to occur using the IPCC<!–[if supportFields]> XE “Intergovernmental Panel on Climate Change (IPCC)” <![endif]–><!–[if supportFields]><![endif]–> 2007 reports.  Europe is projected to warm at a rate between 0.22 and 0.52 Celsius degrees per decade, and precipitation is expected to change with increases in the north of up to 16% and decrease in the south from –4 to –24%.  Scenarios studied by the authors showed decreases in European cropland by 2080 from 28% to 47%.  Heat waves and droughts are also expected to increase in frequency and intensity, leading to reductions in farm income.  The authors find that climate change may have a positive effect in northern areas with increased productivity and range of species, but negative effects in the south.  Crops that currently grow in more southern areas of Europe will become more suitable in the north, and at higher altitudes in the south.  Earlier infestation will be caused by warmer winters, and plant diseases may lead to a greater demand for pesticide<!–[if supportFields]> XE “pesticide” <![endif]–><!–[if supportFields]><![endif]–> use.  Negative effects are seen in livestock as well, with higher mortality risk in livestock systems and an increased disease rate. 
Bindi and Oleson suggest that adaptation strategies will be necessary to manage the negative impacts that climate change is expected to cause to agriculture<!–[if supportFields]> XE “agriculture” <![endif]–><!–[if supportFields]><![endif]–> in the south.  Agricultural activities are a major contributor to greenhouse gas emissions, and mitigation strategies are needed within the agricultural sector.  Soil Organic Carbon stocks in Europe<!–[if supportFields]> XE “Europe” <![endif]–><!–[if supportFields]><![endif]–> will decrease from the increase in temperatures, speeding up organic matter decomposition<!–[if supportFields]> XE “decomposition” <![endif]–><!–[if supportFields]><![endif]–>.  The authors suggest an alternative use for the land that will eventually be unsuitable for crops and relevant to our future needs; land use could change to the production of biofuels and biomaterials from biomass, and reduce our current reliance on fossil fuels.  However, future technical development, including new crop varieties and better agriculture practices, could offset climate change effects. 
Strategies to deal with climate change are discussed, differentiating planned and autonomous adaptations.  Autonomous adaptations may be more feasible, as they are at a smaller scale and occur over a shorter time period.  Examples include changes in crop varieties, sowing dates, and fertilizer<!–[if supportFields]> XE “fertilizer” <![endif]–><!–[if supportFields]><![endif]–> and pesticide<!–[if supportFields]> XE “pesticide” <![endif]–><!–[if supportFields]><![endif]–> use. Comparatively, planned adaptations involve major structural changes, on a large-scale level.  A key planned adaptation available is allocating European agricultural land use differently.  The authors also discuss the concept that organic farming may have a higher resilience to climate change because it has more options for change, but higher costs, and subsidies would be necessary.  

Possibilities and Alternative for Fighting Climate Change and Food Security in Sub-Saharan Africa

Sub-Saharan Africa faces the potential situation of deforestation and land degradation, intersecting with hunger and poverty.  The clearing of forests and woodlands for agricultural use is the primary cause of deforestation.  Agriculture practices can be linked to the climate mitigation strategy of Reducing Emissions from Deforestation and Forest Degradation in Developing Countries (REDD).  Palm et al. (2010) develop four scenarios for increasing agricultural production by differing supplies of nitrogen, and compare the effects to food production, basic caloric needs, and greenhouse gas emissions.  The study found that crop surplus area for reforestation is achieved at low population densities where there is high land availability.  Conversely, to realize food security and reduce greenhouse gases in highly populated areas with small farm sizes, mineral fertilizers are necessary to make land available for reforestation.  The authors believe that agricultural intensification in sub-Saharan Africa with mineral fertilizers, green manures, or improved tree fallows needs policies addressing costs, and incentives to escalate.  The authors suggest carbon financing for small-holder agriculture to reduce emissions due to deforestation.—Whitney Dawson
Palm, C.A., Smukler, S.A., Sullivan, C.C., Mutuo, P.K., Nyadzi, G.I., Walsh, M.G., 2010. Identifying Potential Synergies and Trade-offs for Meeting Food Security and Climate Change Objectives in Sub-Saharan Africa. PNAS 107:46, 19661-19666.

          Palm et al. study how the increase of biological nitrogen (N) and fertilizers from mineral sources can reverse the nutrient depletion in farm soils due to decades of crop harvest and erosion.  Four scenarios for increasing food production are examined in two SSA sites where food security, poverty, and land degradation are high.  The sites differ in rainfall, population density, degree of deforestation, and amount of land used for crops.  The four different N sources are extensification by clearing additional land, fertilizers, green manure through legume cover crops, and improved tree fallow.  Palm et al. used an accounting model for estimating and comparing each scenario to crop productivity, determining if deforestation is needed to meet basic caloric needs or if reforestation is able to occur. 
Ideally, a greater N input directs emissions of nitrous oxide from soils, and yields improve simultaneously, reducing the need to clear forest for food security.  Where landscapes are already heavily used by agricultural production, tree fallows can be used for biomass production to mitigate GHG emissions while still retaining food security.  It is assumed that organic sources of N produce lower emissions than mineral sources, and also lower nitrous oxide emissions.
The study showed that in cases of high population density and small farm sizes, green manure and improved tree fallows do not suffice in achieving necessary crop yields to permit reforestation, and fertilizers are needed to reach food security and reduce greenhouse gas emissions.  However, in lower populated areas, there is more abundance of land, and larger areas for crops to grow.  In these areas, no additional cropland was needed for food security, and yields proved to be highest with fertilizer use, the only scenario that actually freed cropland for reforestation and carbon sequestration.  For each scenario, the N supplied from tree fallow improvement was significantly greater than from green manure.  The global warming potential was only positive where the population densities are lower and reforestation from use of fertilizer was possible.

          Food security requires more than simply meeting the caloric requirement; proper dietary needs, including sufficient proteins and vitamins must be met.  An additional problem for some regions studied in the paper is that agricultural land is utilized for tobacco production rather than food crops.  The authors point out that any change is unlikely to be implemented on a wide scale without significant policy changes, providing incentives for adoption. Interventions are suggested by the United Nations that detail initially subsidizing costly mineral fertilizers, replacing them after a few crop seasons with legume cover crops and agroforestry practices as a source of N. 

Weakening Climate Change and Reaching Food Security Through Soil Carbon Sequestration

There are one billion food-insecure people in the world, with the gap in cereal requirement extremely high in developing regions, and expected to triple by 2015.  Many developing countries are seeking means for reducing this gap, and sustainably increasing grain production.  Carbon Sequestration in soils has potential to mitigate climate change on a global level.  The process results in improvement of soil quality, and therefore also has positive consequences on food security and agronomic productivity.  Farmers that participate in enhancing ecosystem services will receive payments, aiding economic development in developing countries.  In his paper, Rattan Lal (2010) found the technical potential of carbon sequestration in soils to reduce atmospheric carbon dioxide by 50 ppm by the end of the 21st century, increasing the soil carbon pool (SOC) at a rate of 1 Mg/ha/year.  Food security would then be enhanced with cereal and legume production in developing countries increasing by 32 million Mg/year, and roots and tubers increasing by 9 million Mg/year.—Whitney Dawson
Lal, Rattan, 2010. Beyond Copenhagen: Mitigating Climate Change and Achieving Food Security through Soil Carbon Sequestration. Science+Business Media B.V. & International Society for Plant Pathology March, 169–77.

          Rattan Lal found that agricultural soils used by small landholders in the tropic and sub-tropic regions are significantly depleted of their soil organic carbon pool, and highly susceptible to erosion, breakdown, decline in biodiversity, and overall reduction in quality.  Crop yields are therefore very dependant on rainfall patterns, a monsoon easily resulting in crop failure, as seen in India in 2009, due to erosion and structural breakdown.  Though few experiments establishing the relationship of SOC concentration and agronomic yield have been completed, the available data show a strong relationship in areas of diverse soils, and a dramatically stronger relationship for soils of semi-arid regions, such as India.  India would see significant improvement in crop yields in a decade if SOC concentration increased by just 0.1%.  Lal includes an array of data from various studies that continue to prove the strong relationship between SOC concentration and crop yields over every type of climate across the world, including temperate regions.  The gains in agronomic production potentially achieved from increased SOC levels all depend on climate and other factors, but ultimately reduce hunger risks.
          Lal also proves SOC sequestration to be highly cost-effective overall, especially if farmers and land managers were to be compensated for their efforts in sequestering carbon in their soils.  The incentive for farmers to enhance ecosystem services and reduce carbon dioxide levels would be high, as well as the achieving of global food security.  The concept “farming carbon” would be promoted through credits of soil carbon sequestered sold to restore degraded soils, treating these credits as a farm commodity.  Lal argues that “farming carbon” could generate income that would incentivize farmers to invest in soil restoration.
There is a variety of practices that farmers are suggested to take on to enhance the SOC pools that largely involve managing a higher level of nutrients in the soil.  Lal found the optimum range of SOC concentrations in the root zone of soil to be 2–3%, a level at which agronomic yields of crops and pastures would improve if reached.  Farmers in developing countries seeking an alternative to expensive chemical fertilizers can do a number of things to reach these SOC concentration levels such as increasing water capacity, improving nutrient supplies, restoring soil structure, and minimizing soil erosion risks.  Lal concludes that these processes should have been discussed at the Copenhagen COP-15 meeting, as many were disappointed from the lack of multiple benefit strategies considered.  Restoring the SOC pool in depleted cropland soils around the world would benefit the issues of food security, climate change, and soil/environmental degradation.  

The Poverty Implications of Climate-Induced Crop Yield Changes by 2030

The latest IPCC report concluded that the climate is expected to be 1˚C warmer by 2030, regardless of any change in greenhouse gases. Agriculture is the most dependant industry on climate and is expected to be the most impacted.  Although it only accounts for 2.4% of global GDP, agriculture has a much larger share in poor countries and is of great importance.  Past research has not provided decision makers much guidance on who is expected to gain or lose, since it has focused primarily on linking climate impacts on crop yields and agricultural output in given areas; this is somewhat irrelevant on the macro scale due to the interconnectedness from trade.  Hertel et al. 2010 embed disaggregated data on household economic activity within countries in a global trade model to observe how new levels of agricultural productivity from climate change will affect poverty in poor countries.  The models ultimately result in a poor predictor of welfare impacts due to the role that international trade plays in the market, mediating the impacts of climate shocks.  Price increases in agricultural commodities due to changes in the climate may reduce some households’ income level, but may also have a positive effect on those incomes directly related to the agriculture industry.—Whitney Dawson

Hertel, T.W., et al., The Poverty Implications of Climate-induced Crop Yield Changes by 2030. Global Environ. Change (2010), doi: 10.1016/j.gloenvcha.2010.07.001


Hertel et al. 2010 used the Global Trade Analysis Project (GTAP) global trade model, along with its database and poverty modules.  The models have been recently validated by its correct predictions of price impacts from shocks in a previous study.  Effects on agriculture production and poverty implications from climate shocks can be seen in the macro economy with use of these models.  In the study, households were stratified within countries by their primary source of income.  Productivity shocks from climate change were based on six commodities: rice, wheat, coarse grains, oilseeds, cotton, and other crops, and low and high productivity outcome estimates were made.  The low productivity estimates assume rapid temperature change and high impacts, where the high productivity estimates represent slower warming and low sensitivity. 
Coarse grains, such as maize, are expected to see the largest negative outcome, because they are very sensitive to extreme heat.  Wheat and rice yields span zero in any level of productivity, and see gains where climate is currently colder.  Commodity price changes estimated from GTAP are small, with the exception of an expected 15% increase in coarse grain prices.  On a macro level, the most direct impacts of climate change on agricultural losses are on crops in the Sub-Saharan Africa region, and large losses for the US and China are seen as well.  The demand for food throughout the world is mostly inelastic, and the decreases in production produce significant price increases in agricultural commodities.  Some losses in productivity may be offset through international trading, such as in New Zealand and Brazil.  However, the study points out that climate change causes global trade to shrink, therefore resulting in efficiency loss.
While it may be true that rising world prices for staple agricultural commodities could cause a decrease in real income and an increase in poverty, they could also have a more positive effect on changes in earning.  Hertel et al. 2010 also found that although the prices rise by a significant amount, the actual average impact on the cost of living is much more modest.  An increase in earnings is seen for households whose incomes rely on agriculture, where households with incomes completely independent of the agricultural industry have a more negative affected earning level.  This same idea transfers to expectations in poverty levels as well, with a similar lack of symmetry in results and a large variation in poverty impacts across different countries. 
Estimates of climate change impacts did not include the possibility of any adaptations that could reduce negative outcomes, such as introduction of new crop varieties or expanded irrigation infrastructure in a region.  There is also limited knowledge about how global poverty will alter over the next few decades.  Ultimately, climate change impacts on global poverty requires knowledge on both agricultural shocks, and trade patterns, production, consumption, and poverty in certain countries. The magnitude of poverty changes could be detrimental to some developing countries, where those countries with many agricultural self-employed may adversely see a decrease in poverty.

Robust Negative Impacts of Climate Change on African Agriculture

Sub-Saharan Africa (SSA) has the highest proportion of malnourished people in the world, even though its economy is dependant on agriculture production. A major question for the region is how crops in SSA will endure climate change; as to date there have been very limited scientific findings on the topic.  Schlenker and Lobell (2010) use historical crop production and weather data to create a model detailing the crop yield response to the expected change in climate.  The study found that climate change is expected to negatively impact crops in SSA, and substantial investments will be necessary for sufficient agricultural production.—Whitney Dawson 

Schlenker, W., Lobell, D., 2010. Robust negative impacts of climate change on African agriculture. Environmental Research Letters 5, 014010.

          Schlenker and Lobell have created an assortment of models using panel analysis to demonstrate the extent to which SSA agricultural production responds to climate change.  In past studies, availability of reliable data has been a problem, and ‘best-guess’ estimates with large uncertainties have been used.  The models that Schlenker and Lobell designed incorporate historical data of both crop production and weather, and are applied to the staple African crops: maize, sorghum, millet, groundnuts and cassava.  These are thought to be key sources of protein, fat, and calories in the region. Schlenker and Lobell’s use of a data series of historical weather patterns, rather than averaging conditions is advantageous, because infrequent extreme weather events are accounted for.  Their panel data set is preferable to past studies’ methods because it is an observational study, measuring how various constraints affect farmers’ reactions to weather shocks.  The disadvantage to the panel model is that responses to weather shocks may differ from responses to a permanent climate shift.
          The regression model is able to examine how climate change affects the crop yields while keeping all other variables unchanged.  However, farmers in this area tend to use production technologies that are suboptimal due to a lack of resources, and fertilizer is underused in many countries.  Zimbabwe and South Africa have higher fertilizer use, and therefore higher yields, but, as a result are also more susceptible to damage from temperature increases.  Schlenker and Lobell fit separate models for countries that use higher and lower amounts of fertilizer since the responses would be varied.  Although lower fertilizer use results in less of an impact from climate change, the countries using higher amounts of fertilizer still produce higher yields, underlining the importance of sufficient fertilizer use.
The predicted changes in climate were evaluated under 16 climate change models and 1000 randomly drawn years.  Almost all models had significant improvement when the weather variable was excluded from the equation altogether, and predicted negative impacts of warming when it was included, with the exception of the cassava crop, a root crop with a highly variable growing season.  The mean estimates of total changes in production for maize, sorghum, millet, groundnut, and cassava are –22, –17, –17, –18 and –8%, respectively.   
It was found that temperature changes have a significantly stronger impact on crop yields than precipitation changes.  The study omits the possible changes in the distribution of rainfall during growing seasons, which could potentially be important.  Increasing the precision of the climate change forecasts would allow a more confident analysis.  A more regionalized set of data may also prove to be beneficial, however, the broader scale of data analysis can be useful for decision making on the national level.
According to this study, major improvements in agricultural productivity are necessary to combat the substantial poverty problems in SSA.  The study suggests that the challenge of increasing productivity will become more difficult with time due to the warming climate.  The authors suggest that this should be seen as incentive for significant investments in production renovations that will be sustained in the future.  Important investments recommended are crop varieties with greater tolerance to heat and draught, improvement of irrigation systems, disaster relief, and insurance programs to help SSA reach a more sustainable agriculture system.