Focus Corner

How plants may adapt to climate change and help us feed the world

April 6th, 2009 by   (View Author Profile)

Is there going to be enough food for the earth’s expanding population by the end of the 21st Century, when the planet will need to feed some ten billion people? Will there be enough timber to provide wood and the other resources which the world’s population will need by then? These are two questions that have been vexing scientists, which we can condense into one – can plants adapt to climate change.

Some research that will provide some guidance on these questions has been done, but it seems to have been given little publicity. The work has been done as part of the Intergovernmental Panel on Climate Change’s work, which is published every five years in a highly condensed form, which of needs must omit some important findings.

I should first set the context. Most of the food we eat depends directly on growing. Obviously our staples, wheat, corn, rice and potatoes and directly consumed. Our meat is usually got from ruminant animals, like cattle, that eat plant growth. Most of the food chain, I think but cannot be sure, depends ultimately on growing things.

That must mean that while we are busy planning and talking about our low carbon future, we should also be looking at the effect of climate change on growing things, but that directly affects our food and how much we have to eat.

Regardless of any measures that humans may take to cut emissions, the IPCC thinks that we are going to experience a minimum average temperature rise by 2100 of slightly less than one degree Celsius. In fact, having regard to the measures that governments across the world are not taking, the average temperature rise will be more than that, but less us, for the time being assume that we are only dealing with less than one degree rise.

The critical question is perhaps less than obvious, because it is not some much about temperature but by is about carbon dioxide levels. If there will be elevated levels of carbon dioxide in the atmosphere how will this affect plant growth?

One study at the University of California at San Diego has shown that plants can adapt to rising carbon dioxide levels. It seems that an increased carbon dioxide level in the air indicates that plants can and will adapt, by opening and closing the leaf stomata, which is the mechanism that plants use for taking in and expelling gases. The studies did not show that plants will actually grow faster or better as a result of having more carbon dioxide, which is what many people thought.

Instead the plants are likely to take what they need, not more. It seems to follow that in order to use plant to help sequestrate carbon dioxide, we need more of them, rather than expecting them to do more work than they have evolved to do.

Results of another experiment involving soya beans have also been published. This study was in natural conditions, rather than in laboratory conditions, and might ell explain the other function that plants have which releases carbon dioxide into the atmosphere. It was conducted by the Soybean Free Air Concentration Enrichment facility at Illinois. As well as drawing carbon dioxide and making sugars for growth in the process of photosynthesis, plants respire out carbon dioxide, like most living things.

Until recently no one understood whether plants would respire more (oxygen in and carbon dioxide out) as atmospheric carbon dioxide content increased, or less, or whether the respiration levels would remain the same. There was scientific support for each scenario.

The soya bean experiment indicates that in levels of carbon dioxide concentrations at 550 parts per million (the present concentration is 386ppm, but 550ppm is not inconceivable by 2050) plants expired 37% more than they did in today’s atmospheric conditions.

The greater amount of respiration may well mean that plants will be breathing more because they are expending more energy – on growing. If that is the right conclusion to draw, then it may be that the inevitably increased carbon dioxide levels may result in being able to grow more plants for food.

We do not know yet for certain, but if that is the case we have some way of feeding the world at the end of the century, providing other climate changes – such as drought, flooding and desertification – do not prevent us from doing so.

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