Combating Climate Change: An Agricultural Perspective

The difference lies in whether ribulose-1,5-bisphosphate carboxylase—oxygenase RuBisCO within the plant cells is saturated by CO 2 or not. The RuBisCO enzyme is highly conserved in plants and as such it is thought that the response of all C 3 crops including wheat and soya beans will be comparable. Theoretical estimates suggest that increasing atmospheric CO 2 concentrations to ppm, could increase photosynthesis in such C 3 crops by nearly 40 per cent Long et al. The physiology of C 4 crops, such as maize, millet, sorghum and sugarcane is different. Thus, rising CO 2 concentrations confer no additional physiological benefits.

These crops may, however, become more water-use efficient at elevated CO 2 concentrations as stomata do not need to stay open as long for the plant to receive the required CO 2. Thus yields may increase marginally as a result Long et al. Many studies suggest that yield rises owing to this CO 2 -fertilization effect and these results are consistent across a range of experimental approaches including controlled environment closed chambers, greenhouse, open and closed field top chambers, and free-air carbon dioxide enrichment FACE experiments Tubiello et al.

Some authors argue that crop response to elevated CO 2 may be lower than previously thought, with consequences for crop modelling and projections of food supply Long et al.

3 ways farmers can combat climate change

Plant physiologists and modellers alike recognize that the effects of elevated CO 2 , as measured in experimental settings and subsequently implemented in models, may overestimate actual field and farm level responses. This is because of many limiting factors such as pests and weeds, nutrients, competition for resources, soil water and air quality which are neither well understood at large scales, nor well implemented in leading models.

Despite the potential positive effects on yield quantities, elevated CO 2 may, however, be detrimental to yield quality of certain crops. For example, elevated CO 2 is detrimental to wheat flour quality through reductions in protein content Sinclair et al.

Without CO 2 fertilization, many regions, especially in the low latitudes, suffer a decrease in productivity by In contrast, by including CO 2 fertilization all but the very driest regions show increases in productivity. The two projections show the impact of including CO 2 physiological effects and are the members of the ensemble with the most positive and negative changes in productivity averaged over all global croplands. Global-scale comparisons of the impacts of CO 2 fertilization with those of changes in mean climate Parry et al.

However, regions such as Africa and India are nevertheless still projected to experience up to 5 per cent losses by , even with strong CO 2 fertilization. These losses increase to up to 30 per cent if the effects of CO 2 fertilization are omitted. In fact without CO 2 fertilization all regions are projected to experience a loss in productivity owing to climate change by However, existing global scale studies Parry et al.

Reproduced from Parry et al. A reduction in CO 2 emissions would be expected to reduce the positive effect of CO 2 fertilization on crop yields more rapidly than it would mitigate the negative impacts of climate change. Stabilization of CO 2 concentrations would therefore halt any increase in the impacts of CO 2 fertilization, while the impacts of climate change could still continue to grow.

Therefore in the short term the impacts on global food production could be negative. However, estimates suggest that stabilizing CO 2 concentrations at ppm would significantly reduce production losses by the end of the century Arnell et al. For all species higher water-use efficiencies and greater root densities under elevated CO 2 in field systems may, in some cases, alleviate drought pressures, yet their large-scale implications are not well understood Wullschleger et al.

This could offset some of the expected warming-induced increase in evaporative demand, thus easing the pressure for more irrigation water. Soil moisture and run-off may be more relevant than precipitation and meteorological drought indices as metrics of water resource availability, as these represent the water actually available for agricultural use. These quantities are routinely simulated by physically based climate models as a necessary component of the hydrological cycle. Importantly, the scenarios with an increase in mean run-off and the greatest increase in available soil moisture included the effects of CO 2 fertilization in the model, while those with a decrease in mean run-off and the smallest increase in soil moisture availability did not include this effect Betts et al.

Two projections of future change in soil moisture as a fraction of that required to prevent plant water stress over global croplands for year means centred around and , relative to — Positive values indicate increased water availability. The two projections are the members of the ensemble with the most positive and negative changes in annual mean run-off averaged over all global croplands. Two projections of percentage change in time spent under meteorological drought as defined in terms of soil moisture in global croplands for year means centred around and , relative to The two projections are the members of the ensemble with the greatest and least percentage change averaged over all global croplands.

Ozone is a major secondary air-pollutant, which at current concentrations has been shown to have significant negative impacts on crop yields Van Dingenen et al. Whereas in North America and Europe, emissions of ozone precursors are decreasing, in other regions of the world, especially Asia, they are increasing rapidly Van Dingenen et al. Ozone reduces agricultural yield through several mechanisms. Firstly, acute and visible injury to products such as horticultural crops reduces market value.

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Secondly, ozone reduces photosynthetic rates and accelerates leaf senescence which in turn impacts on final yield. In Europe and North America many studies have investigated such yield reductions e. However, in other regions, such as Asia, little evidence currently exists.

Thus, our understanding of the impacts in such regions is limited.

Combating climate change : an agricultural perspective (eBook, ) [www.newyorkethnicfood.com]

Anthropogenic greenhouse gas emissions and climate change have a number of implications for agricultural productivity, but the aggregate impact of these is not yet known and indeed many such impacts and their interactions have not yet been reliably quantified, especially at the global scale. An increase in mean temperature can be confidently expected, but the impacts on productivity may depend more on the magnitude and timing of extreme temperatures. Mean sea-level rise can also be confidently expected, which could eventually result in the loss of agricultural land through permanent inundation, but the impacts of temporary flooding through storm surges may be large although less predictable.

Freshwater availability is critical, but predictability of precipitation is highly uncertain and there is an added problem of lack of clarity on the relevant metric for drought—some studies including IPCC consider metrics based on local precipitation and temperature such as the Palmer Drought Severity Index, but this does not include all relevant factors. Agricultural impacts in some regions may arise from climate changes in other regions, owing to the dependency on rivers fed by precipitation, snowmelt and glaciers some distance away.

Drought may also be offset to some extent by an increased efficiency of water use by plants under higher CO 2 concentrations, although the impact of this again is uncertain especially at large scales. The climate models used here project an increase in annual mean soil moisture availability and run-off in many regions, but nevertheless across most agricultural areas there is a projected increase in the time spent under drought as defined in terms of soil moisture. Moreover, even the sign of crop yield projections is uncertain as this depends critically on the strength of CO 2 fertilization and also O 3 damage.

Few studies have assessed the response of crop yields to CO 2 fertilization and O 3 pollution under actual growing conditions, and consequently model projections are poorly constrained.

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Indirect effects of climate change through pests and diseases have been studied locally but a global assessment is not yet available. Overall, it does not appear to be possible at the present time to provide a robust assessment of the impacts of anthropogenic climate change on global-scale agricultural productivity. National Center for Biotechnology Information , U. Author information Copyright and License information Disclaimer.

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4. Implications of climate change for agricultural productivity in the early twenty-first century?

While the Government Office for Science commissioned this review, the views are those of the author s , are independent of Government, and do not constitute Government policy. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This article has been cited by other articles in PMC.

Abstract This paper reviews recent literature concerning a wide range of processes through which climate change could potentially impact global-scale agricultural productivity, and presents projections of changes in relevant meteorological, hydrological and plant physiological quantities from a climate model ensemble to illustrate key areas of uncertainty. Introduction Agriculture is strongly influenced by weather and climate. Direct impacts of climate change on agriculture a Changes in mean climate The nature of agriculture and farming practices in any particular location are strongly influenced by the long-term mean climate state—the experience and infrastructure of local farming communities are generally appropriate to particular types of farming and to a particular group of crops which are known to be productive under the current climate.

Open in a separate window. Selected tropical cyclones of the past decade, and their agricultural impacts. Indirect impacts of climate change on agricultural productivity a Pests and diseases Rising atmospheric CO 2 and climate change may also impact indirectly on crops through effects on pests and disease. Non-climate impacts related to greenhouse gas emissions: Conclusions Anthropogenic greenhouse gas emissions and climate change have a number of implications for agricultural productivity, but the aggregate impact of these is not yet known and indeed many such impacts and their interactions have not yet been reliably quantified, especially at the global scale.

A meta-analytic review of the responses of photosynthesis, canopy. Change 53 , — doi: Policy 9 , — doi: Nature , — doi: Science , — doi: Tellus 59 , — Berthier E. Bioscience 57 , — doi: In Climate change Cambridge University Press Ciais P. Cambridge University Press Ding Y. Change 54 , — doi: Cambridge University Press Evans N. Interface 5 , — doi: Estimating changes in crop productivity. In press Climate impacts on European agriculture and water management in the context of adaptation and mitigation—the importance of an integrated approach. B , — doi: Change 74 , — doi: Finnish Environment Institute Holland G.

World Meteorological Organization Holton J. Cambridge University Press Juen I. Change 59 , 37—48 doi: The importance of temperature relative to precipitation. Treatment of major food crops with elevated carbon dioxide or ozone under large-scale fully open-air conditions suggests recent models may have overestimated future yields. Change 70 , — doi: Cambridge University Press Morgan P. A meta-analysis of photosynthesis, growth and yield. In addition, he has edited two well-received books. He has chaired several crop breeding sessions and delivered invited lectures at national and international conferences.

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Summary The effects of climate change can already be felt around the world, and they will likely impact all facets of human civilization—from health, livelihood security, agricultural production, and shelter to international trade. Table of Contents Foreword M. Editor s Bio Editor. Reviews "Experts consider plant pathogens, plant disease, insects and more as they consider the latest options for handling future climates. Request an e-inspection copy. Your Web browser is not enabled for JavaScript. Some features of WorldCat will not be available.

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Implications of climate change for agricultural productivity in the early twenty-first century

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