Agriculture in a dry climate

UK PlantSci conference addresses food security as drought increases

With much of England officially in drought, we are getting a taste of the challenges we may increasingly face due to climate change. Drought has the potential to decrease crop yields, reduce food security and damage farmers’ livelihoods. The UK PlantSci conference at the John Innes Centre on the Norwich Research Park will demonstrate the diverse ways plant scientists in Norwich and across the UK are tackling the problem of drought, so we can rise to the challenge of reducing hunger in a growing population.

Professor Jim Beynon is Chair of the newly-founded UK Plant Sciences Federation (UKPSF) and part of the organising team for UK PlantSci conference. He says: “It takes between 2,000 and 5,000 litres of water to produce one person’s daily food intake. We often think of crop improvements as the amount of crop we can get per area of land, but in many instances water is the limiting factor. We don’t just need to increase crop yield in relation to land area but also the amount of crop produced per unit of water used in irrigation – the ‘drop per crop’.”

Farmers in parts of the UK are already facing water restrictions, and the situation in Mexico shows the extent of problems drought can cause. Severe drought in Mexico that has already cost farmers over a billion dollars in crop losses and the government has allotted $2.65 billion in emergency aid.

Professor Beynon says: “If we are going to grow crops in dry conditions one possibility is to change the way they respond to drought, rather than add more water. Improving plants’ tolerance to stress will be crucial to future gains in crop productivity.”

Plants regulate water loss and take up the gases they need through tiny pores called stomata. Research is underway at the John Innes Centre to make stomata more responsive to drought conditions. In collaboration with Jordanian scientists, Dr Wendy Harwood is studying guard cells that control the opening and closing of stomata in response to stress. The findings will be applied to local Jordanian varieties of wheat, which are grown on over half of cultivated land in the country.

Drought and other forms of physical stress are expensive for plants, using up valuable energy. Understanding energy metabolism in plants, and improving its efficiency, will help researchers produce crops that are better able to deal with stress. This will ensure their yields suffer less as a result of water shortages.

Dr Matthew Hannah, a Research Program Leader at Bayer CropScience studying plant stress tolerance, is speaking at the conference. He says: “The challenge facing agriculture is to grow enough food and energy crops in light of increasing world population, competition for arable land, water scarcity and climate change. If we want to meet these challenges we need to improve crop varieties.”

Ever since our ancestors began cultivating crops, farmers have changed the characteristics of plants through selective breeding. These changes in plant genes have greatly increased yields. A plant’s characteristics, however, are not just determined by the sequence of DNA or by their environment. As well as the DNA sequence, the structure of the DNA molecule is important, determining which genes are switched on or off.

Changes in the structure of the DNA, called epigenetics, can be passed from one generation of plants to the next, even though they are not stored in the DNA sequence. During long periods of drought, genes involved in the plant’s response can be switched on and off through changes to the structure of the DNA. The epigenetic structure of DNA can pass these characteristics from one generation to the next. Scientists at Bayer CropScience have already shown that the efficiency of energy use affects yield in canola, a seed used to produce oil for food or, increasingly, biodiesel. In his talk at UK PlantSci Dr Hannah will discuss the potential for using epigenetics to produce drought-tolerant plants.

He says: “To grow well in drought conditions different genes need to be activated. Rather than changing the genes, our work alters the DNA structure so different genes are activated. There’s great potential here to produce crops which need less water.”

An alternative to improving plants’ response to drought is to provide them with conditions where plants can thrive with much less water. Irrigation is the founding pillar of modern agriculture, but has come at a price. Groundwater depletion has greatly increased since 1950, particularly in the past decade. This won’t just have a negative impact on irrigation levels; it also causes problems such as increases in salinity and drinking water contamination. To address these problems, Charlie Paton, Managing Director of Seawater Greenhouse, is using the world’s largest supply of water: the oceans.

Seawater Greenhouses are being used in dry regions including Australia, Tenerife and Oman, and new projects are underway in Cape Verde and Abu Dhabi.

Charlie explains his technology: “Seawater is pumped over a honeycomb of cardboard ‘sponges’ which cool and humidify the ventilation air. Water is essential to plant growth and seawater also contains valuable nutrients, so it is perfect for irrigation. The only problem is the high level of salt it contains. The salt, however, is very useful in itself. Air entering the greenhouse is filtered through the evaporator ‘sponge’ which is wet with concentrated saltwater. The salt kills pathogens, reducing the need for fungicides, and the salt can also be sold for industrial or domestic markets. It’s a win-win situation and given its abundance, seawater is impossible to over exploit.”

Many regions facing drought also have the problem of high temperatures. The process of evaporation requires energy, so the air entering the greenhouse is cooled. This means cooler temperatures conducive to plant growth are achieved without the need for energy input.

Charlie says: “Conventional agriculture is a highly extractive process, which in many regions has become unsustainable. We need a paradigm shift to move to a restorative system. Around the world ever deeper boreholes are dug in order to increase crop yields through irrigation. Where ground water is extracted at a rate that is faster than natural replacement, the benefit is short lived. In the long run it makes the situation worse.”