The UN’s Intergovernmental Panel on Climate Change has just published the world’s most comprehensive study in seven years of the impact climate change has (and will have) on the world’s natural environment. Diversified farming, including agroforestry, may help mitigate the effects and food production, writes Patrick Worms.
Patrick Worms is the Brussels-based Science Policy Adviser of the Nairobi-based World Agroforestry Centre.
For the first time, the IPCC has found that climate change has “already affected agriculture, human health, ecosystems on land and in the oceans, water supplies, and some people’s livelihoods,”
Perhaps most worrisome is its finding that maize and wheat, the world’s most important food groups, are increasingly affected: “Periods of rapid food (…) price increases following climate extremes (…) indicate a sensitivity of current markets to climate extremes,” says its summary report. The threat of falling yields and rising prices is looming.
This is not surprising. Crop plants, like humans, have preferred temperature and humidity ranges at which they thrive. The productivity of maize, by far the world’s most important crop, falls off a cliff when it is exposed to temperatures above 38°C. And such temperatures are already becoming more common across the globe, as droughts and heat waves become more frequent.
The bad news seemingly keeps on piling up. And yet Professor Chris Field, co-chair of the working group that produced the report, spoke of “exciting opportunities” in Yokohama last Sunday. That may seem surprising. But “understanding those challenges and tackling them creatively can make climate-change adaptation an important way to help build a more vibrant world in the near-term and beyond,” he said. Agriculture offers a key example.
Back in the 1960s, the world was also facing a food crisis. India and other countries, it was feared, would soon fall victim to giant famines thanks to runaway population growth. Hundreds of millions would die. And yet none of this ever came to pass. The Green Revolution package – hybrid seeds, chemical fertilizers, irrigation and phytosanitation – boosted farm productivity to levels previously unseen.
That revolution was based on the science of its time. Farming was optimised to produce a few crops cosseted in vast numbers on large, monotonous fields. This model still feeds the world, but is showing its limits. Chemical fertilizers are made with natural gas, a fossil fuel; tractors and irrigation pumps run on diesel. Both generate greenhouse gases. Aquifers are over-exploited. Soil microorganisms suffer from the intensive use of weedkillers and pesticides. And vast fields of single crops are uniquely exposed to extreme weather: there is nothing to protect crops from strong winds, hard rains, droughts or heatwaves.
Science has moved on. The evidence is clear: in agriculture as in so much else, complexity promises a resilience to extremes which fragile monocrop systems can’t match. Farmers know that producing many different crops protects them from the price swings in any one of them, and that planting several varieties rather than a single one is a protection against disease wiping out one’s crop. Likewise, scientists now know what to do to make farming generally more resilient to climate change.
Climate smart agriculture brings together a range of measures designed to “increase sustainable productivity, strengthen farmers’ resilience, reduce agriculture’s greenhouse gas emissions and increase carbon sequestration,” according to the World Bank. Agroforestry is a promising suite of climate smart techniques where trees and crops are farmed together, often on the very same field.
Take maize. Planting it with shade trees protects it from extreme temperatures, bringing better yields. Using nitrogen-fixing trees, common in the tropics, can boost yields still further – in some cases, by over 200% – and reduces fertilizer input costs.
Similar stories can be told for many crops, from wheat to coffee. Adding the right trees makes the fields where they are grown more resilient to extreme weather, and their farmers less dependent on a single crop. In France, for example, wheat-walnut combinations are spreading: the trees protect the crops, and the valuable timber is prized. In Germany and elsewhere, cereals are grown with trees raised for biomass energy. In Sumatra, rubber agroforest gardens can generate up to three times the income of rubber plantations, in part because of their much lower need for costly pesticides. And across Africa, cocoa and coffee grown under shade trees generate your wake-up drink as well as your evening treat.
Because trees can pump up moisture through their root system, they lessen the impact of droughts. And their leaf and twig litter improves the soil’s fertility, making it more conducive for farming. The cherry on the cake? Trees capture vast amounts of carbon dioxide as they grow, locking it up in their trunks, branches and roots. They don’t just help farmers adapt to climate change: they mitigate it too.
Agroforestry is a more complex form of agriculture: some of the systems used in the margins of tropical rainforests involve dozens of useful species. That complexity partly explains why, despite its promise, it is still used by a minority of farmers only. Agroforestry demands long-term planning, since trees take years to grow. It demands skills, such as pruning, normally never taught to farmers. And it demands a very different approach to the management of fields and pastures.
But that complexity should not scare us. In science, the twenty-first century is the century of complexity. From cosmology to sociology, the sheer powers of modern information technologies allow us to tackle questions that were hitherto unanswerable. That the same can happen in agriculture is a source of hope in a changing world.