Tim Hess

Climate change impacts on crop productivity in Africa and South Asia

Climate change is a serious threat to crop productivity in regions that are already food insecure. We assessed the projected impacts of climate change on the yield of eight major crops in Africa and South Asia using a systematic review and meta-analysis of data in 52 original publications from an initial screen of 1144 studies. Here we show that the projected mean change in yield of all crops is 8% by the 2050s in both regions. Across Africa, mean yield changes of 17% (wheat), 5% (maize), 15% (sorghum) and 10% (millet) and across South Asia of 16% (maize) and 11% (sorghum) were estimated. No mean change in yield was detected for rice. The limited number of studies identified for cassava, sugarcane and yams precluded any opportunity to conduct a meta-analysis for these crops. Variation about the projected mean yield change for all crops was smaller in studies that used an ensemble of >3 climate (GCM) models. Conversely, complex simulation studies that used biophysical crop models showed the greatest variation in mean yield changes. Evidence of crop yield impact in Africa and South Asia is robust for wheat, maize, sorghum and millet, and either inconclusive, absent or contradictory for rice, cassava and sugarcane.

Rainfall trends in the North East Arid Zone of Nigeria 1961–1990

Abstract Daily rainfall records for 1961–1990 for Nguru (12.53°N, 10.28°E, alt. 343 m), Potiskum (11.42°N, 11.02°E, alt. 415 m) and Maiduguri (11.51°N, 13.05°E, alt. 354 m) in Nigeria and Maine Soroa (13.13°N, 11.58°E, alt. 339 m) in Niger were analysed to describe any changes in season duration, rain-days per season and rainfall amount per rain-day. There was a consistent decrease in annual rainfall of 8 mm year −1 at all four stations. The majority of this reduction occurred in August or September. Although there was a delay in the onset of the rains at the two westernmost stations, the main reason for the decrease in rainfall was a reduction of 6–25 days in the number of rain-days during the rainy season. This increased the mean duration of dry spells during the rainy season by up to 1.5 days. No change in the average rainfall per rain-day was detected except at Maine Soroa where there was a slight reduction. The results are discussed in terms of their implications for sustainable agriculture in the region.

Climate change and water in the UK - past changes and future prospects

Climate change is expected to modify rainfall, temperature and catchment hydrological responses across the world, and adapting to these water-related changes is a pressing challenge. This paper reviews the impact of anthropogenic climate change on water in the UK and looks at projections of future change. The natural variability of the UK climate makes change hard to detect; only historical increases in air temperature can be attributed to anthropogenic climate forcing, but over the last 50 years more winter rainfall has been falling in intense events. Future changes in rainfall and evapotranspiration could lead to changed flow regimes and impacts on water quality, aquatic ecosystems and water availability. Summer flows may decrease on average, but floods may become larger and more frequent. River and lake water quality may decline as a result of higher water temperatures, lower river flows and increased algal blooms in summer, and because of higher flows in the winter. In communicating this important work, researchers should pay particular attention to explaining confidence and uncertainty clearly. Much of the relevant research is either global or highly localized: decision-makers would benefit from more studies that address water and climate change at a spatial and temporal scale appropriate for the decisions they make.

Applications of crop/soil simulation models in tropical agricultural systems☆

Abstract Crop simulation models have been used widely to describe systems and processes at the level of the genotype, the crop, the farming system, the region, and the global environment, but examples of how the use of such models has benefited poor people in developing countries are limited. There is, therefore, an urgent need to make the use of models in research more relevant to problems in the real world and to find effective means of disseminating the results from work using models to the potential beneficiaries. To achieve this, we believe that there must be a shift in the thinking of crop/soil modelers toward making people more center stage and toward a more problem-solving approach. This means researchers must think of the real problems faced by ordinary people in developing countries and construct and apply their models to contribute to solving these problems. For this to be effective, modelers need to define clearly who are the end users of their models and to enter into dialogue with these people so that the final product is tailored to their needs. There appear to be two opposite directions in which further crop modeling research can develop. On the one hand, in response to the rapidly expanding field of genomics, links between information at the gene level and performance at the phenotype level need to be established, and methodologies to do this must be developed. Such models will have the potential to contribute to enhancing the efficiency of crop improvement programs worldwide by providing more efficient ways of identifying and evaluating desirable characteristics for specific plant breeding goals. On the other hand, crop models need to be incorporated into higher order systems such as the whole farm, catchment, or region. Some progress has already been made in linking crop growth models with other physical process models to improve our understanding of how changes in agricultural systems influence overall environmental impacts. However, the role of people in these systems also needs to be made explicit so that the day-to-day decisions that they make to sustain and improve their livelihoods and the influence these decisions have on their environment and natural resource base can be taken into account.

A microcomputer scheduling program for supplementary irrigation

Abstract A real-time irrigation scheduling computer package for use on farms is described. The package comprises four models; a reference crop evapotranspiration model, an actual evapotranspiration model, a soil water balance model and an irrigation forecast model. The models used have been shown to produce reliable estimates of the soil water balance, however, the predictions are sensitive to the accuracy of the input data measured on the farm. This paper summarises the experience of applying such a program to supplementary irrigation in the UK.

Identifying future risks to UK agricultural crop production: putting climate change in context.

Internationally, agriculture is widely regarded as one of the sectors at most risk from a changing climate. This is due to the impact of increased temperatures, reduced rainfall and increased frequency of extreme events, not only in the tropics but also in temperate environments. In the UK, growers also face a range of ‘non-climate’ risks, which, it is often argued, present a potentially greater and more immediate threat to sustainable food production than climate change. This paper highlights the climate and non-climate impacts on crop production, the adaptation options and the institutional and regulatory barriers to their uptake by farmers. It concludes that there are likely to be both positive impacts (for example, yield gains) and negative impacts (for example, increased water stress). Either way, there will be a need for new investments in adaptive management and technology, including new collaborations between the public and private sectors, to enable UK agriculture to respond to the potential effects of climate change.

Water balance and water use of pearl millet-cowpea intercrops in north east Nigeria

Abstract An experiment was conducted in North East Nigeria to examine the water balance and water use of intercrops of pearl millet and two cowpea varieties as well as sole crops of the same cultivars. The crops were grown on a sandy loam soil in a spatial arrangement typical of husbandry practices of the region. The soil is characterised by rapid drainage and low water-holding capacity. Results indicate that intercropping cowpea with millet did not increase the water use rate over sole millet as transpiration by cowpea may be substituting for soil evaporation. Root zone water storage after the millet harvest was sufficient to maintain a long duration cowpea cultivar that was able to make use of water that otherwise would have been lost to drainage during the dry season. As there was no evidence of water stress up to millet harvest, intercropping cowpea with millet increased the efficiency of utilisation of rainfall. It is concluded that water supply may not be the most limiting constraint on agricultural production in such conditions. The implications of these findings for agriculture in the region are discussed.

Synergies and trade-offs in the management of lowland rural floodplains: an ecosystem services approach

Abstract Priorities for the management of lowland rural floodplains in many parts of Europe have changed from a focus on agricultural production towards multi-functional landscapes that provide a range of environmental, social and economic benefits to society. This paper uses an ecosystem services framework to explore alternative management scenarios with different objectives (production, biodiversity, floodwater storage, agri-environment and income) for two rural floodplains in England. Each scenario featured different types of land cover and hydrological management. The results revealed the key role of the hydrological regime in shaping ecosystem service provision in floodplains. Both conflicts and synergies were apparent. Scenarios with deep water tables and low flood frequencies had high scores for agricultural production and flood storage capacity, but low scores for environmental outcomes. Scenarios with shallow water tables and frequent flooding showed high scores for environmental and cultural outcomes, but at the cost of a reduced flood storage capacity and increased flood risk. The scope for multiple benefits has implications for the realignment of policies to realize extra value from floodplain ecosystems. Editor Z.W. Kundzewicz; Guest editor M.C. Acreman Citation Rouquette, J.R., Posthumus, H., Morris, J., Hess, T.M., Dawson, Q.L. and Gowing, D.J.G., 2011. Synergies and trade-offs in the management of lowland rural floodplains: an ecosystem services approach. Hydrological Sciences Journal 56 (8), 1566–1581.

The ecological research needs of business

Summary 1. Businesses have an unrivalled ability to mobilize human, physical and financial capital, often manage large land holdings, and draw on resources and supply products that impact a wide array of ecosystems. Businesses therefore have the potential to make a substantial contribution to arresting declines in biodiversity and ecosystem services. To realize this potential, businesses require support from researchers in applied ecology to inform how they measure and manage their impacts on, and opportunities presented to them by, biodiversity and ecosystem services. 2. We reviewed papers in leading applied ecology journals to assess the research contribution from existing collaborations involving businesses. We reviewed applications to, and grants funded by, the UK’s Natural Environment Research Council for evidence of public investment in such collaborations. To scope opportunities for expanding collaborations with businesses, we conducted workshops with three sectors (mining and quarrying, insurance and manufacturing) in which participants identified exemplar ecological research questions of interest to their sector. 3. Ten to fifteen per cent of primary research papers in Journal of Applied Ecology and Ecological Applications evidenced business involvement, mostly focusing on traditional rural industries (farming, fisheries and forestry). The review of UK research council funding found that 35% of applications mentioned business engagement, while only 1% of awarded grants met stricter criteria of direct business involvement. 4. Some questions identified in the workshops aim to reduce costs from businesses’ impacts on the environment and others to allow businesses to exploit new opportunities. Some questions are designed to inform long‐term planning undertaken by businesses, but others would have more immediate commercial applications. Finally, some research questions are designed to streamline and make more effective those environmental policies that affect businesses. 5. Business participants were forward‐looking regarding ecological questions and research. For example, representatives from mining and quarrying companies emphasized the need to move beyond biodiversity to consider how ecosystems function, while those from the insurance sector stressed the importance of ecology researchers entering into new types of interdisciplinary collaboration. 6.  Synthesis and applications. Businesses from a variety of sectors demonstrated a clear interest in managing their impacts on, and exploiting opportunities created by, ecosystem services and biodiversity. To achieve this, businesses are asking diverse ecological research questions, but publications in leading applied ecology journals and research council funding reveal limited evidence of direct engagement with businesses. This represents a missed opportunity for ecological research findings to see more widespread application.

Meta-analysis of climate impacts and uncertainty on crop yields in Europe

Future changes in temperature, rainfall and soil moisture could threaten agricultural land use and crop productivity in Europe, with major consequences for food security. We assessed the projected impacts of climate change on the yield of seven major crop types (viz wheat, barley, maize, potato, sugar beet, rice and rye) grown in Europe using a systematic review (SR) and meta-analysis of data reported in 41 original publications from an initial screening of 1748 studies. Our approach adopted an established SR procedure developed by the Centre for Evidence Based Conservation constrained by inclusion criteria and defined methods for literature searches, data extraction, meta-analysis and synthesis. Whilst similar studies exist to assess climate impacts on crop yield in Africa and South Asia, surprisingly, no comparable synthesis has been undertaken for Europe. Based on the reported results (n = 729) we show that the projected change in average yield in Europe for the seven crops by the 2050s is +8%. For wheat and sugar beet, average yield changes of +14% and +15% are projected, respectively. There were strong regional differences with crop impacts in northern Europe being higher (+14%) and more variable compared to central (+6%) and southern (+5) Europe. Maize is projected to suffer the largest negative mean change in southern Europe (−11%). Evidence of climate impacts on yield was extensive for wheat, maize, sugar beet and potato, but very limited for barley, rice and rye. The implications for supporting climate adaptation policy and informing climate impacts crop science research in Europe are discussed.