Monday, October 05, 2015

Improving Crop Yields to Respond to Global Warming and Population Growth

A couple of weeks ago there was an article in The Economist titled "Agricultural biodiversity: Banks for bean counters". I quote extensively from the article:
Climate change is expected to cause higher temperatures and more frequent droughts, changing the distribution of pests and diseases. Population growth will add to the pressure on productive land: the UN expects the number of people in the world to rise from 7.3 billion today to 9.7 billion by 2050. This, together with a switch to more meat-eating, will mean a big increase in the demand for food. The UN Food and Agriculture Organisation (FAO) says humanity will need 70% more food by then.
Dependence on a few staples worsens the consequences of any crop failure. Just 30 crops provide humans with 95% of the energy they get from food, and just five—rice, wheat, maize, millet and sorghum—provide 60%. A single variety of banana—Cavendish—accounts for 95% of exports. A fast-spreading pest or disease could see some widely eaten foodstuffs wiped out. 
That makes it even more important to preserve the genetic diversity found in crop wild relatives and traditional varieties as an insurance policy. Alas, much of it has already disappeared. The FAO estimates that 75% of the world’s crop diversity was lost between 1900 and 2000. As farming intensified, commercial growers favoured a few varieties of each species—those that were most productive and easiest to store and ship. 
According to Cary Fowler of the Global Crop Diversity Trust, an international organisation based in Germany, in the 1800s American farmers and gardeners grew 7,100 named varieties of apple. Today, at least 6,800 of them are no longer available, and a study in 2009 found that 11 accounted for more than 90% of those sold in America. Just one, “Red Delicious”, a variety with a thick skin that hides bruises, accounts for 37%. 
Meanwhile urbanisation, pollution, changing land use and invasive species are threatening the crop wild relatives that survive. A study in 2008 concluded that 16-22% of those related to peanuts, potatoes and cowpeas (a legume grown in semi-arid tropics) will have vanished by 2055 as a result of climate change.
So what if climate does change? Don't you just grow the same crops a few miles further from the equator? Well, what if the soils are different. What if there is not as much water in the new spot as the old one? What if you were on the western side of a hill, and the new spot is on the southern side, and the light conditions are different? What if there are different pests and diseases in the new spot? What if your machinery won't work as well in the new spot as it did in the old? I think that the world will need a lot of crop improvement to produce new varieties of major crops that will produce well under the new conditions.

One solution is pretty much out of the question. Most of the arable land is already in agricultural production. The world will no longer solve its food needs by putting unused arable land into production.

We could not do a lot be simply rationalizing our distribution and use of food. Obesity is harmful to the health of the obese as well as wasteful of food, and should be reduced globally.  Cows are a very wasteful way to produce protein as compared with legumes, and the fat intensive diet found in the USA not only uses a lot of land to feed cattle, a lot of grain to fatten them, but also results in poor health in people who have too much fat in their diet. It would be great if the world could rationalize protein production, getting those who eat too much animal protein to stop doing so, increasing the production of vegetable protein, and distributing protein more appropriately so that fewer people are protein starved and fewer people eat too much of the wrong kinds of protein.

Ultimately, we will have to have better varieties of food crops, and that means varieties with genes that better suit them to produce well in the places that they will be planted. Those genes can come from already domesticated plants, or from the much larger source in non-domesticated species. They can be transferred into new varieties of crops by mass transfers of genes as in traditional plant breeding, and then subjected to a long process of selection to weed out the genes that don't improve the variety. Alternatively they can be transferred by much more scientific and efficient processes of biotechnology. Society will choose. but I think I know the better way.

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