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Using climate-smart cropping systems to respond to climate change

By increasing global temperatures and changing precipitation patterns, climate change will affect the distribution and productivity of crops. In a collaborative study, scientists at INRA Occitanie-Toulouse, INRA Nouvelle-Aquitaine-Bordeaux, and CIRAD sought to describe climate-smart cropping systems that can confront and adapt to the challenges presented by climate change. The results were recently published in EDP Sciences.

Rice terraces in the far north of Vietnam—Nicolas Bertrand @INRA. © INRA
Updated on 11/16/2017
Published on 08/24/2017

The three researchers leading the project assert that climate-smart cropping systems must simultaneously reduce greenhouse gas emissions, adapt to climate change, and promote food security. The agricultural industry has been exploring several ways of dealing with climate change: limiting greenhouse gas emissions, increasing carbon sequestration, and producing renewable energy. The study described here focused on the first two options.

An important figure

Agriculture, forestry, and other types of land use account for 24% of greenhouse gas emissions, which means they also present opportunities for reducing emissions.

Moving toward lower-emission cropping systems

Nitrous oxide (N2O) and methane are the main greenhouse gases released by agricultural systems. According to the study, the best way of limiting N2O emissions is to limit the use of nitrogen fertilisers. Crop yields could be maintained in other ways: by carefully calculating the actual fertiliser levels needed, making better use of organic materials such as crop residues, or spacing out fertiliser applications over time. Furthermore, because fertiliser production is energy intensive, an additional indirect reduction in emissions would result from lower fertiliser use. Another possibility is to introduce legumes into cropping systems since legumes can fix atmospheric nitrogen, resulting in a diminished need for nitrogen fertilisers. The main source of methane is rice farming. Methane emissions by rice farms could be reduced significantly by changing irrigation regimes. Instead of keeping rice fields submerged, they should be dried out mid-season or intermittently irrigated.

The study evaluated several approaches to increasing carbon sequestration: the best known is no-till farming. However, as the researchers stress, emissions of all greenhouse gases must be considered in the evaluation process. For instance, no-till farming can lead to increased N2O emissions. Other methods could sequester greater amounts of carbon in biomass or soils without hurting yields. They include the use of cover crops, hedgerows, or agroforestry.

Adapting to climate change

Dealing with climate change also means learning to adapt. The study found that shifting sowing dates to account for changes in the growing season and the harvest period is the easiest and cheapest adaptation technique. Using more diverse crops in the rotation cycle can help increase farm resilience in response to unexpected climatic events. To maintain crop yields, it may seem logical to simply increase irrigation levels, but this solution may be problematic in the longer term because water availability will become more uncertain and a source of conflict. Over the longer term, it would be better to focus on breeding plant varieties better suited to emerging water- and temperature-related constraints.

Considering trade-offs and the unintended effects of different solutions

Finally, the researchers looked at the compatibility of different measures for reducing emissions and adapting to climate change. Notably, they examined the potential unintended consequences for the environment and biodiversity. Certain solutions could prove to be antagonistic, and compromises will need to be made. The study has especially highlighted that climate-smart cropping systems will need to adopt a global approach incorporating multiple criteria.

REFERENCE

Philippe Debaeke, Sylvain Pellerin, Eric Scopel. Climate-smart cropping systems in temperate and tropical agriculture: mitigation, adaptation and trade-offs. Cahiers Agricultures 26, 34002. (Des systèmes de culture climato-intelligents pour les agricultures tempérées et tropicales : atténuation, adaptation et compromis.)