Ensuring food supplies amid the challenge of climate change

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Media captionEmma Simpson puts the grapes to the test

Climate change isn't something we think about as we fill up our trolleys in the supermarket aisles. But it's an issue that worries the boss of Asda who has to make sure his supply chain is able to keep the produce flowing onto the shelves.

Securing fresh fruit and veg all year round is already a complicated global business for our big grocers.

Take a look at some of the labels and you'll find asparagus from Peru, bananas from the Caribbean and kiwis from Chile, to name but a few. We consumers, of course, take all this choice for granted.

Asda is one the few big retailers to attempt to map the risks from a changing climate. It found that 95% of its fresh produce could be at risk in the years ahead.

"Climate change is a big industry and a big global issue, and we've been working hard to understand them so we can try to get ahead," says Andy Clarke, Asda's CEO.

"We've seen, over the course of the last decade, rising temperatures across the world."

Asda, is working with its suppliers", he says, "so that the customer isn't affected in the way in which they could be".

Drier summers

Availability of water, or lack of it, is the major worry. Take oranges, for instance.

It is a product that we can't grow in the UK so the supermarkets rely on countries like Spain to produce our citrus fruit.

Southern Spain is a Mediterranean breadbasket producing a whole host of fruit and veg. It's been hit by droughts and water is already in short supply.

Image caption UK supermarkets rely on countries like Spain to produce citrus fruit

And farmers are noticing the hot, dry summers are getting longer.

"It seems that over the last decade or so, the autumn and spring seem to be disappearing," says Antonio Martinez, an agronomist who helps run one of the biggest orchards in Murcia, in south eastern Spain.

"Before in September and October it would start to rain and the trees would get their water from the autumn rain. We now need to irrigate all the way through the autumn as if it's still summer"

Mr Martinez's farm, Rio Tinto, is unusual. Their orchards were created out of reconverted mining land and they are taking a different approach to growing fruit. Instead of packing as many trees as possible into every last inch of soil, they've introduced new ways of cultivation.

For instance, there are pine trees as well as orange trees dotted across the valley to create a more natural habitat. For this farm, it's all about managing what they've got in a way that's sustainable.

And that includes water.

Each tree needs around 25 litres (5.5 gallons) of water to produce just one orange. Here they make sure they don't waste a single drop.

Water meters, trialled by Asda, have been installed. With electric sensors, they measure just how much water the soil needs.

"All over the farm, we know exactly where we need to put the water. This new technology helps to counteract the lack of rainfall," says Mr Martinez.

He hopes this will future-proof the farm against the risks of climate change.

Image caption Each orange tree needs around 25 litres (5.5 gallons) of water to produce just one orange

Fruit and veg from Spain need to keep flowing in the years ahead; if not, supermarket prices will rise because there will be less supply to meet demand.

"We need to prepare because everything about agriculture depends on the water and unless you're prepared for this lack of rainfall then you're doomed to fail."

Soil risk

Farmers in the UK are being warned that they need to do more to prepare their land for a changing climate.

It is all about the soil.

More than two million tonnes of top soil is already being eroded every year, degraded in some areas by intensive farming practices.

Climate change is likely to result in more extreme weather - from hotter, drier summers to severe rainstorms which could accelerate soil erosion.

Farming in some of the most productive parts of the country like East Anglia is at risk, says the government's independent Committee on Climate Change.

"Farmed soils in the Fens might lose all of their rich peat topsoil in the next 30 to 60 years," it reported.

The UK could become more reliant on imported food, at a time of growing worldwide demand, if farmers don't make their soil more resilient to extreme weather, the committee found.

Image caption Spain? Italy? California? in fact, this is Kent

Some farmers are already making their soil more resilient. Andrew Lingham has given up ploughing much of his land in Kent which means it doesn't lie bare between harvests. Instead he covers it with cover crops, like tillage radish, to protect and improve the soil:

"After heavy rain I've noticed that the soil is able to absorb the water much better. I'm not seeing any soil erosion at all, no soil running out the gate and down the road.

"Historically, we've been moving the soil too much. We used to move the ground three times before we put a seed in. My key phrase is less is more. I don't know why more people don't do it," he says.

"We need to start taking steps to reduce the loss of soil organic matter."

Home-grown grapes

Yet climate change may also bring some opportunities, such as longer growing seasons and the introduction of new crops.

Just a few miles down the road from Mr Lingham's farm, the first table seedless grapes have just been grown in the UK.

Asda hopes this trial could see UK grapes on supermarket shelves by 2018.

Image caption These are the first UK-grown grapes "that people can actually eat," says Asda's Alberto Goldbacher

"We've seen real success in grapes for wine, particularly in this area of Kent, so we started a trial three years ago to see if we could produce a seedless table grape that people could buy and eat," says Asda's Alberto Goldbacher.

"We had no idea if we could get any production, we've identified varieties we want to take further."

More challenges

Ironically, it is climate change which will help make this method viable.

"If we do get warmer, drier summers it makes it more straightforward for the grapes to grow. We currently import grapes from 15 different countries," he says.

"We see there are seasonal gaps and believe the UK could meet some of those gaps, for instance in October or November, when we start to import from countries in South America, that's a much shorter supply chain and is more environmentally friendly."

That may be.

But climate change will create many more challenges than opportunities for the grocery industry and UK supermarkets as they strive to provide us with the same choice on our plates all year round at prices we can afford.

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