Plants hold the key to removing atmospheric carbon dioxide. Can we make them more efficient carbon storers and feed the planet in the process?
The farmers and scientists I spoke to are trying to solve a very important problem: how can agriculture reduce its environmental impact, and perhaps even one day be used to reverse climate change?
Crops, like all plants, draw carbon dioxide (CO2) from the atmosphere during the process of photosynthesis, which they use to generate stores of energy from sunlight. Some of that carbon is fixed in the soil, where it will remain if left untouched. Plants are part of a once balanced system that saw carbon cycling in and out of natural reservoirs in the land, sea, atmosphere and living things. So, could farmers redress the balance by using the vast amount of crops and land needed to feed us, as carbon sinks that capture and store carbon in the ground?
I asked Paul Hawken, the author behind Project Drawdown, which has modelled the 100 most substantive solutions to reversing global warming, why we need to rethink the carbon cycle. He says it is a misunderstanding to think of carbon as pollution – rather, it is part of a cycle that is out of balance.
The carbon stored on Earth vastly outweighs the carbon in our atmosphere. There is more than three trillion tonnes of carbon in farmlands, grasslands, forests, mangroves and wetlands – that is four times as much carbon as in the atmosphere, Hawken told me, adding that if we are able to increase stored carbon by 9% on Earth, just on the land, we will have sequestered all the carbon that humans have emitted since 1800. Hawken raises an interesting point: terms like ''carbon offsetting'' and ''net zero'' are commonly used, but to reverse the effects of climate change we will need to go beyond that by storing more carbon than we emit into the atmosphere.
James Wong visits farms at the cutting edge of research (Credit: BBC)
And that doesn't include carbon stored in marine and aquatic systems. While visiting Portugal, I saw another innovator planting kelp forests to store carbon and perhaps one day be used as a food source. Kelp, the largest species of seaweed, is a type of photosynthesising algae and not a plant.
By cutting open sections of their leaves, kelp spores can be harvested, dried, cooled and sprayed onto gravel which is then dropped into the sea. These stones, coated in kelp spores, then seed an underwater forest which only takes a few months to grow, quickly working to sequester carbon on the seabed.
Returning to dry land for a moment, I also had the privilege of visiting researchers at the University of Illinois's Ripe project, which is experimenting with the way plants grow. Photosynthesis is a process that has evolved over millions of years. So, it's strange to think that we could make the process better, but that is exactly what Lisa Ainsworth, the deputy director of Ripe, and her colleagues are trying to do.
For example, in a field of plants, only the uppermost leaves photosynthesise at maximum efficiency. The leaves lower down are blocked are in the shadow of the leaves higher up, and so they receive less sunlight and don't photosynthesise as well. In fact, the lowest leaves might even contribute to carbon emissions (like animals, plants also respire, breathing in oxygen through their leaves and 'exhaling' carbon dioxide).
Follow the Food is a multimedia series by BBC Future and BBC World News that investigates how agriculture is responding to the profound challenges of climate change, environmental degradation and rapidly growing populations that face our global food supply chains. Follow the Food traces emerging answers to these problems – both high-tech and low-tech, local and global – from farmers, growers and researchers across six continents.
