Impacts of Climate Change on Agro-Ecosystems and Food Security in Africa. A Review.

Kennedy W. Nyongesa1, Francis O. Obiria2 , Bernard S. Omuya2

1 Institute for Climate Change and Adaptation (ICCA), University of Nairobi

2 Kisii University


Agriculture is extremely vulnerable to climate change. Increased temperature eventually reduces yields of desirable crops while promoting weed infestation and proliferation of pest. Decline in precipitation increase the likelihood of crop failures and exacerbate food insecurity. Although there could be gains in some crops in some regions of the world, the overall impacts of climate change on the Agro-ecosystems are expected to be negative, threatening food security. The continued dependence of crop production on light, heat, water and other ecological and climatic factors warrants the need for a comprehensive consideration of the potential impacts of climate on global agriculture. Tropics are more dependent on agriculture compared to the temperate regions and therefore more valuable to climate change. Hydrological regimes in which crops grow will surely change with global warming; climate change will also have an impact on the soil, a vital element in agricultural ecosystems. Higher temperatures will increase evapotranspiration and soil temperatures which increase chemical reactions rates and diffusion controlled reactions. While crops could be impacted by climate change, it is likely that farm animals would will be ever more susceptible to change in climate. It is expected that increased air temperatures will cause more heat stress to livestock. Livestock are endodermic hence they are affected by increased heat and humidity. During stifling heat livestock reproduction declines as well as appetite due to hormonal changes.  Decreased appetite will lengthen the time needed for livestock to reach their target weight. Heat stress can also increase fighting among animals. This theoretical review paper encapsulates these concepts in conceptual framework. A conclusion is drawn illustrated by a conclusive working model.

Key Words:  Climate Change, Agro-Ecosystems, Agriculture, Food Security 

This paper was presented at the 11th Egerton University Conference and Peer- reviewed, corrected and recommended for publication : Dates: 29 – 31 March, 2017 “Knowledge and Innovation for Social and Economic Development. ”


Agro-ecosystems are ecological systems modified by human beings in order to produce food or other agricultural products (Conway, 1987). The agro-ecosystems in the Highveld region of South Africa  produce 70% of the country’s commercially grown cereal crops, with 90% of its maize being cultivated there (du Toit et al., 2000). The sustainability of the maize producing agro-ecosystems is of huge consequence to food security in South Africa and to the well-being of the rural economy of the Highveld. Chambers (1997) recognizes that humans are at the centre of agro-ecosystems and that their well-being is a key issue for the sustainability of agro-ecosystems. Sustainability is applying long term perspectives, in regard to human well-being and ecological integrity, to policies and actions. (Walker and Schulze, 2006). This definition of sustainability is used by the authors in this paper. The sustainability of agro-ecosystems in Africa will be influenced, inter alia by climate change and by land use changes and related factors resulting from the above two (Hansen and Jones, 1996).

The inter-relationships between social, economic and environmental influences are associated with sustainability, a systems approach to sustainability is therefore essential (Ikerd, 1993). For such a systems approach, a framework was adapted with a goal-orientated system. Incorporating Hansen and Jones (1996) method to characterize sustainability, the framework has the following four steps: 1. Goal definition; 2. Sustainability modeling; 3. Evaluation strategy and 4. Making recommendations that are predictive, with constraints to sustainability being identified.  Hansen (1996) considers it necessary to characterize the concept of sustainability when using it to identify constraints, to identify research foci and for policy development. A case in point is the influence of El Nin˜o on the seasonal rainfall in the Highveld region in South Africa,  a reality for farmers (du Toit and Prinsloo, 1998), since it influences directly both their economic security in the long term and local food security in the shorter term.

Literature Review

Linkage between Agro-ecosystems, Land use Changes and Climate Change

Olson et al. (2004) observe that expansion of cultivation in many parts of East Africa has changed land cover to more agro-ecosystems; food production in Kenya, for example, is reported to have increased steadily between 1980 and 1990. In East Africa, natural vegetation cover has given way not only to cropland, native or planted pasture.

 Further, Olson et al. (2004) posit that land use changes in East Africa has also experienced the expansion of urban centers and urban population between 1960 and 2000; during the last few decades the area under cultivation more than doubled in Kenya and Tanzania, but in Uganda the change has been moderate. In Mbeere, in Kenya cultivation expanded by 70% between 1958 and 2001, leaving only isolated pockets of forest and bush. Similarly, in Tanzania, report a significant expansion of cultivation in the Moshi area over the same period. However, in Uganda, agriculture only expanded in the drier rangelands, not in the wetter highlands.

Globally, there was realization that land surface processes influence climate and that change in these processes impact on ecosystem goods and services (Antrop, 2000). The impacts that have been of primary concern are the effects of land use changes on biodiversity, soil degradation and the ability of ecosystems to support human needs (Alcamo, et al., 2005). The sequence of land cover and land use change in East Africa is complex (Mugisha, 2002). In some places pastoralists modify wooded landscapes into more open landscapes by burning, the changes are quite subtle and pastures can quickly revert to bush land and woodland when burning ceases (Olson et al., 2004).

Campbell et al. (2003) observe that land use changes and climate variations influence each other. Numerous studies have shown that land use changes and climate variations affected the structure and function of ecosystems and then affected the supply of ecosystem services (Olson et al., 2004). Land use changes might increase provision and value of some services but decrease others (Antrop, 2000). The effects of land use changes and climate variations may increase changes in ecosystem services delivery (Alcamo, et al., 2005). As to the impacts of climate variations on human wellbeing, it can aggravate the situation for food security by increasing risks of crop failure because of the higher frequency of extreme events and progressive changes of climate (Sivakumar and Brunini, 2005). In addition, as some ecosystem services decline, some new human actions, such as the excessive use of fertilizers and pesticides, have had adverse impacts on ecosystems and further on human wellbeing (Power, 2010, McCarthy et al., 2001).

Hydrological Regimes, Climate Change, Water Security and Food Security

Hydrological regime refers to changes with time and space in rates of flow of rivers and in levels and volumes of water in rivers, lakes, reservoirs marshes and other water bodies. A hydrological regime is closely related to seasonal changes in climate (Cowx, 2000). In regions with a warm climate, the hydrological regime is affected mainly by atmospheric precipitation and evaporation; in regions with a cold or temperate climate, the air temperature is a leading factor (Nilsson and Berggren, 2000).

The hydrological regime of rivers consists of a number of characteristic periods (phases) that vary with seasonal changes in the conditions under which rivers are fed (Nilsson and Berggren, 2000). These phases are known as high water, freshet, and low water. Rivers are fed unevenly in the course of a year because of varying amounts of precipitation and uneven melting of snow and ice and entry of their water into the rivers (Cowx, 2000). The fluctuations observed in the water level are caused mainly by changes in the flow rate and by the effects of wind, ice, and man’s economic activities (Kundzewicz et al., 2007).

Cowx, 2000 posits that the hydrological regime of lakes is determined by the relationship between the amount of precipitation reaching the lake’s surface, evaporation, surface and underground flow into the lake, and surface and underground outflow of water from the lake, as well as by the size and shape of the lake, the pattern of change in the surface area with change in level, and wind activity, which determines the size of the waves and the extent to which the level rises and falls. Kundzewicz et al., 2007 conclude that the hydrological regime of marshes is dependent on climatic and hydrological conditions, terrain, and the nature of the vegetation. Nilsson and Berggren (2000) observe that man’s economic activities are introducing ever greater changes in hydrological regimes.

The impact of climate change on the quantity and quality of groundwater resources is of global importance because 1.5–3 billion people rely on groundwater as a drinking water source (Kundzewicz and Döll, 2009). There has been very little research on the impact of climate change on groundwater (Kundzewicz et al., 2007). Studies of Global Climate Models (GCMs) projects significant changes to regional and globally averaged precipitation and air temperature, and these changes will likely have associated impacts on groundwater recharge (Kurylyk and MacQuarrie, 2013). Studies show that agricultural yield will likely be severely affected over the next hundred years due to unprecedented rates of changes in the climate system (Jarvis et al., 2010; Thornton et al., 2011). In arid and semi-arid areas the expected precipitation decreases over the next century would be 20% or more.

According to UNEP (2004), the world experienced unprecedented high-impact climate extremes during the 2001–2010 decade that was the warmest since the start of modern measurements in 1850. In 1955, only seven countries were found to be with water stressed conditions. In 1990 this number rose to 20 and it is expected that by the year 2025 another 10–15 countries shall be added to this list. It is further predicted that by 2050, 2/3rds of the world population may face water stressed conditions (Gosain et al., 2006); majority of the Arab countries depend on the international water bodies for their requirements.

UNESCO (2004)  reports that the Nile river basin is the home of approximately 190 million people of Ethiopia, Eritrea, Uganda, Rwanda, Burundi, Congo, Tanzania, Kanya, Sudan and Egypt. Since majority of nations of the Nile river basin are among the top 10 poorest countries of the world therefore it is absolutely difficult for them to adopt any strategy of water management, which require investment. The OSS (Observatory of the Sahara and the Sahel) regions, which have the least natural water resources, both in absolute terms and in relation to its population will be affected severely. Over 90% of Sub-Saharan Africa agriculture is rain-fed, and mainly under smallholder management (Batino et al., 2011). de Wit and Stankiewicz (2006) identify three river systems in Africa: the areas receiving very low rainfall have virtually no perennial drainage (dry regime), then the areas with an intermediate range in which drainage density increases with increasing rainfall (intermediate rainfall regime) and the areas of high rainfall (high rainfall regime). The dry regime covers the largest area of the African continent, approximately 41%; the intermediate rainfall regime which covers approximately 25% because this is the area where changes to precipitation would result in serious changes in drainage supply. Further, as predicted by an ensemble of global climate change models by the second part of this century, climate change would directly affect African countries, 75% of which belongs to the intermediate stage. Fig. 1 shows the present rainfall regimes in Africa and Fig. 2 shows the expected changes in the precipitation by the end of the 21st century on the basis of composite leading fully coupled GCMs adapted by IPCC for forecasting purposes (CSAG, 2002). A net 2.5 °C rise in temperature in Africa will result in a decline of net revenues from agriculture by US$ 23 billion (Kurukulasuriya and Mendelson, 2007).

Fig1: Precipitation in the African continent at the end of 20th century

Source: de Wit and Stankiewicz, 2006

Fig 2: Predicted changes in the precipitation in the African continent due to climate change at the end of the 21st century

Source: de Wit and Stankiewicz, 2006).

The shortage of water can be augmented from wastewater utilization after suitable treatment (FAO, 2012). Water recycling by giving technological support can speed up can help in minimizing the impact of climate change on crop yield and water resources (de Wit and Stankiewicz (2006).

The Relationships between Soils, Climate Change and Food Security

Soils are important to food security and climate change has the potential to threaten food security through its effects on soil properties and processes (Brevik, 2012). It requires an understanding of how climate and soils interact and how changes in climate will lead to corresponding changes in soil (Pimentel, 2006). Respective of soils and climate change interactions are the carbon and nitrogen cycles because C and N are important components of soil organic matter (Brady and Weil, 2008); because carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are the most important of the long-lived greenhouse gases (Hansen, 2002). Human management of soils can have a profound impact on the balance of C and N gas emissions from those soils, and therefore influences global climate change (Post et al., 2004).

The largest active terrestrial C pool is in soil, which contains an estimated 2,500 Pg of C compared to 620 Pg of C in terrestrial biota and detritus and 780 Pg of C in the atmosphere (Lal, 2010). Carbon is readily exchanged between these pools; therefore, they are called active pools. In addition to the active pools, there are approximately 90,000,000 Pg of C in the geological formations of Earth’s crust, 38,000 Pg of C in the ocean as dissolved carbonates, 10,000 Pg of C sequestered as gas hydrates, and 4,000 Pg of C in fossil fuels (Pimentel,2006).  However, most of the C in these pools is locked up over long periods of geologic time and not readily exchanged; leading to these pools being referred to as inactive pools (Post et al., 2004); the release of C from the inactive pools, particularly though the combustion of fossil fuels is also an important anthropogenic source of greenhouse gases. Soils naturally sequester C through the soil-plant system as plants photosynthesize and then add dead tissues to the soil (Post and Kwon, 2000). Carbon is also naturally emitted from soils as CO2, CO and CH4 gases due to microbial respiration (Brady and Weil, 2008). Soil management techniques such as no-till systems may result in lower CO2 emissions from the soil and greater C sequestration in the soil as compared to management systems based on intensive tillage (Brevik, 2012).

However, other management changes such as using cover crops, crop rotations instead of monocropping, and reducing or eliminating fallow periods can lead to C sequestration in soil; as can returning land from agricultural use to native forest or grassland(Brevik, 2012). Sequestration of C tends to be rapid initially with declining rates over time (Dixon-Coppage et al., 2010). Most agricultural soils will only sequester C for about 50–150 years following management changes before they reach C saturation (Mosier, 1998).

The C and N cycles are key parts of the global climate system, and soils are an integral part of these cycles (Post and Kwon, 2000). Agriculture contributes a particularly large percentage of annual anthropogenic CH4 emissions to the atmosphere (Mosier, 1998).  Agriculture contributes CO2, CH4, and N2O into the atmosphere; hence management systems have the potential to influence climate change (Dixon-Coppage et al., 2010). The interactions between soils and the atmosphere in a changing climate are important variables as we seek to understand climate change and its potential influence on food security through the biogeochemical cycles (Pimentel, 2006).

Food systems, Food security and the link to Climate Change

Food security depends on robust food systems that encompass issues of availability, access and utilization, not production alone and consequently that the nature of key research issues changes as more questions related to food security are formulated (Ingram et al., 2005).  There are several definitions of what constitutes food systems each formulated in relation to a specific range of issues such as globalization of the agri-food systems (Goodman, 1997); community food systems (Gillespie and Gillespie ,2000); ecological interests (Barling, 2004).

Ingram et al. (2005) posits that food systems are defined as a set of dynamic interactions between and within the biogeophysical and human environments which result in the production, processing, distri­bution, preparation and consumption of food. They encompass components of: (i) food availability; (ii) food access and (iii) food utilization.

Access to culturally acceptable food Food systems may be simple, as in the case of a subsistence farmer who produces processes and consumes food on farm. Ingram et al. (2005) conclude that intensification of agricultural production, since the 1940s has been accompanied by profound changes in the organization of food systems around the world including changes in distribution, marketing, affordability and preferences for particular food items.

Food systems around the world are changing very rapidly as urbanization and globalization proceeds apace (Ingram et al., 2005). The urbanization of many predominantly rural countries in the last three decades has been accompanied by the rapid growth of supermarkets in many countries, often accompanied by foreign investment by global retail chains (Reardon et al., 2003). However, even in African countries such as Kenya, supermarkets have grown from a tiny niche market in 1997 to be greater than 20% of urban food retailing today (Neven and Reardon, 2004). Success within Kenya is now spreading to other East African countries with important effects on the market conditions faced by farmers including the decline of traditional wholesalers and the increase in direct purchases from larger farms.  Table 1 shows changes in the supply of fresh fruit and vegetables to the Uchumi supermarket chain in Kenya by supplier type for the period 1997–2008.

Table 1: Changes in the supply of fresh fruit and vegetables to the Uchumi supermarket chain in Kenya by supplier type for the period 1997–2008.

Type of supplier Vegetables Fruits
1997 2003 2008 1997 2003 2008
small farms 13 10 15 5 10 10
medium farms 10 25 30 10 10 10
large farms and plantations 5 15 35 0 15 35
traditional brokers/wholesalers 70 45 10 70 40 10
imports 2 5 10 15 25 35

The values are the percentage contribution to the total supply.

Source: Neven and Reardon, 2004.

According to Gregory and Ingram (2000), climate change may affect food systems in several ways ranging from direct effects on crop production to changes in markets, food prices and supply chain infrastructure.  For example in southern Africa, climate is among the most frequently cited drivers of food insecurity because it acts both as an underlying, ongoing issue and as a short-lived shock. Because of the multiple socioeconomic and biophysical factors affecting food systems and hence food security, the capacity to adapt food systems to reduce their vulnerability to climate change is not uniform across regions (Jones and Thornton, 2003). Several reviews have further assessed the potential consequences of changes in climate on the growth and yield of crop plants (Amthor, 2001); their  linkage to plant physiological processes hence concluding that the earlier-anticipated benefits of C02 fertilization would be largely offset by nutrient limitations, pollutants and further interactions with climatic factors (Long et al., 2005). This, and other similar projections that use a process-based crop production model to link climate change to crop yield can then be modeled for a uniform crop yield and up scaled to a larger area normally within some form of geographic information system (GIS). Figure 3 shows the three components of food systems with their main elements.

Figure 3: The Three Components of Food Systems with their Main Elements Source: Gregory and Ingram, 2000.  

Misselhorn (2005) observes that, to better address the food security concerns that are central to economic and sustainable development agendas, it is desirable to develop a broader research framework, which integrates biophysical and socio-economic aspects of food systems and thereby addressing two key questions:

(i)Which aspects of food systems are most vulnerable to climate change?

(ii) What can be done to reduce the vulnerability of these food systems and thereby improve food

In studies of household food security in southern Africa, climate was one of some 33 drivers mentioned as important by householders (Misselhorn, 2005). It has become clear that the key to assessing vulnerability is to develop research frame-works which can explicitly consider the social and political constraints which condition the capacity of food systems to cope with external stressors such as climatic change (Mustafa, 1998). Finally, changes in the food systems aimed at reducing vulnerability feedback to environmental and societal changes themselves may reinforce agricultural practices that either reduce or exacerbate land degradation, and increase or reduce farm profitability (Adger, 1999; Scholes and Biggs, 2004). According to Gregory and Ingram (2000) not all food systems are equally vulnerable to environmental changes. Human vulnerability and poverty are often inter­related because both the likelihood of exposure to stresses is greater among the poor and because a large proportion of their resources are spent either purchas­ing or producing food, thereby reducing their capacity to cope with perturbations (Hume et al., 2001). Regional policy decisions do not always convert to successful local implementation especially if distri­bution services are inadequate, or food preferences are ignored (Ellis, 2003). The following adaptation actions are illustrated below using an example from each of the three elements of the food system as depicted in figure 1. (a) Reducing food system vulnerability by increasing food production: Past increases in agricultural production have occurred as a result of both extensification (altering natural ecosystems to generate products) and intensification (producing more of the desired products per unit area of land already used for agriculture (Gregory and Ingram, 2000). In future, intensification will be the dominant means for increasing production although the cultivation of new land will be important in some regions (e.g. an estimated contribution of 47% from extensification in sub-Saharan Africa to cereal production by 2020 (Alexandratos, 1995). (b) Reducing food system vulnerability by improving food distribution: Pingali and Khawaja (2004) assert that infrastructural and non-infrastructural controls on food distribution can be significant impediments to reducing food system vulnerability in a timely manner. This became strikingly apparent during the drought relief effort mounted in 1990/1991 in southern Africa in response to the estimated 86 million people at risk in the region of whom some 20 million were deemed at serious risk. Food availability for the region was severely con­strained due not to lack of food per se but by lack of investment in distribution systems and institutional constraints. This brief summary highlights several ways in which regional food insecurity could be reduced, and shows that adaptation options caninclude arange of issues including, among others, regional investment in port, rail and grain storage infrastructure and in region-wide political agreements to facilitate the flow of food in an emergency. (c) Reducing food system vulnerability by increasing economic access to food: In the case ofsouthern Africa, Arfitzen et al. (2004) indicates that the discussioncenters on varied means.  According to Mahendra Dev et al. (2004); first, price mechanisms and policies could be designed that serve the interest of producers and consumers. Second, regional specialization in food production and regional trade would lower production costs and food prices and, therefore, improve access. Third, economic growth will lead to income and employment generation, both of which will facilitate access to food. Finally, stability in political governance supported by an effective pool of human and institutional resources facilitates the establishment and maintenance of food systems. Figure 4 shows the conceptual framework as envisaged in this review, depicting the main drivers of Food Insecurity in Africa. This conceptual framework can be adopted for research.

Figure 4: The Conceptual Framework that shows that the Interrelationships between the Aspects that Determine Food Insecurity.

Source: Nyongesa, Obiria and Omuya, 2017

Agro-ecosystems may be strongly influenced by projected increase in atmospheric CO2 concentration and associated climate change (Reilly, et al., 1996). The direct effect of increasing CO2 concentration on plant growth is of particular interest because of the possibility of increasing crop yields in the future once the substrate for photosynthesis and the gradient of CO2 concentration between atmosphere and leaf will increase (Reid, et al., 2005). Current atmospheric CO2 concentration (about 360 µmol mol-1) is insufficient to saturate the ribulose 1, 5-bisphosphate carboxylase (Rubisco), the enzyme responsible for primary carboxylation, the metabolic process that drives photosynthesis, in C3 plants (Sivakumar and Brunini,  2005); very few studies indicate a yield depression at elevated CO2 concentration and those are primarily with flower crops.

Probably the most important physical effect of transpiration in plants is the cooling that takes place at the transpiring surface (Sivakumar and Brunini, 2005). Because large quantities of energy are required in the phase change from liquid to vapor, evaporation provides a very efficient mechanism for heat dissipation.

An Overview of Impacts of Climate Change on Livestock Productivity

Thornton et al. (2007) posit that the situation in Africa and other developing countries is that generally, climate can affect livestock directly and indirectly. Although indirect, feed resources can have a significant impact on livestock productivity, the carrying capacity of rangelands, the buffering ability of ecosystems and their sustainability, and the distribution of livestock diseases and parasites In Africa the main pathways in which climate change can affect the availability of feed resources for livestock are as follows:

1. Land use and system changes can lead to different compositions in animal diets and to alteration in the ability of smallholders to manage feed deficits in the dry season (Thornton et al., 2007).

2. Changes in the primary productivity of crops, forages and rangelands are probably the most visible effect of climate change on feed resources for ruminants with the end result, for livestock production, a change in the quantity of grains, stovers and rangelands available for dry season feeding (Thornton et al., 2007).

3. Changes in species composition in rangelands and some managed grasslands will have significant impact on the types of animal species that can graze them, and may alter the dietary patterns of the communities dependent on them (Thornton et al., 2007).

4. The quality of plant material will be altered (from C3 to C4) by increased temperatures and will reduce the digestibility and the rates of degradation of plant species which will lead to reduced nutrient availability for animals (Thornton et al., 2007).

4. However, increased levels of CO2 may favour C3 plants; it is also possible that C4 grasses may be replaced with C3 grasses owing to increased levels of CO2 (Taub, 2010); or climate change may result in the deterioration of pasture towards lesser quality sub-tropical C4 grasses.

Climatic changes directly influence livestock health through a number of factors, including the range and abundance of vectors and wildlife reservoirs, the survival of pathogens in the environment, and farming practice (Gale et al, 2009; Semenza and Menne, 2009). Transmission of zoonotic diseases occurs when there is an overlap of activities between reservoir, vector and humans; changes in climate may impact on all of these factors involved in disease transmission and interactions (Gray et al, 2008; Randolph, 2008a). Abiotic factors, such as temperature and day length, impose constraints on when and how ticks quest for hosts (Randolph, 2008b). Beyond vector-borne diseases, intestinal nematodes develop in soil, and factors such as soil humidity and temperature have a strong influence on developmental rates (Brooker et al., 2002). Direct effects are also related to radiation, the animal’s inability to dissipate environmental heat causes heat stress (Fuquay, 1981; Bucklin et al., 1992). Evaporation is the most important methods of heat transfer as it does not depend on a temperature gradient (Ingram and Mount, 1975). Humidity affects the evaporation rate; therefore, the temperature humidity index (THI) becomes relevant under conditions of high temperature and high humidity (Thom, 1958).

Theoretical Analysis

Compiling and analyzing the results of more than 770 reports about the CO2 enrichment on the economic yield of 24 agricultural crops and 14 other species, Jarvis et al. (2010) showed that only 39 out of 437 separate observations (i.e. 9%) yielded less than their respective controls and the average relative increase was 28% considering all of the crops or 36% excluding flowers. The effect of CO2 enrichment on flower yield was generally lower than on food crops. Mean yield increases were 23%, 32%, 42%, 54% and 52% for fruit, cereal C3, leaf, legume and root crops, respectively. Hansen (2002) estimated that a doubling CO2 concentration, holding other factors constant, could lead to a 34 ± 6% increase in agricultural yields of C3 plants and a 14 ± 11% in C4 plants with a 95% confidence interval. Gregory et al., 2005 concluded that provided adequate water, nutrients and pest control, yields of C3 and C4 crops growing in about 700 µmol CO2 mol-1 would be about 30 to 40% and 9%, greater than present yields, respectively. Below-ground growth is also increased at elevated CO2 concentration

Application: Suggested Adaptation Mechanisms

Food systems, underpin food security, which is the state achieved when food systems operate such that all people, at all times, have physical and economic access to sufficient, safe and nutritious food to meet their dietary needs and food preferences for an active and healthy life (McClain-Nhlapo, 2004); food security is diminished when food systems are stressed. For the future, continued technological developments are anticipated to facilitate the adaptation of crops to changing environments (Gregory et al., 2005).

There are many plant characters and elements of crop management that contribute to the efficient use of water by crops (Gregory, 2004), but relatively little attention has been paid to root characters that may allow more water to be exploited or used more efficiently, largely because root systems are very difficult to measure. However, genotypic differences are known to exist in many features of root systems which may be exploitable to improve crop yield in drier climates (O’Toole and Bland, 1987). Studies with existing genotypes in dry areas may inform the adaptation possible under conditions of changed climate (Champoux et al., 1995). Porter and Semenov (2005) posit that the development of DNA-based molecular markers has opened up opportunities for identifying the genetic factors (quantitative trait loci) underpinning various root traits. Again, this science is at an early stage of development for root traits, but significant progress has been made in studies of drought tolerance with rice (Babu et al., 2001).  In reducing food system vulnerability by increasing economic access to food, this important adaptation is as yet hardly pursued, but should gain momentum with trade liberalization and policy shifts towards food security.


Studies on the impacts of Land use changes and climate variations on ecosystem provisioning services and the impacts of provisioning services changes on human wellbeing will provide scientific and theoretical basis for global policy making especially focusing on food security. At present, our understanding of how changes in climate will influence the C and N cycles is incomplete, meaning additional research into these questions is needed.  Notably, it has become necessary now to take very seriously the impact of climate change on the present water resources and take necessary actions without any further delay; because food grows where water flows.


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