Is agroforestry a lemon?

Agroforestry is a promising alternative to conventional, and damaging, agricultural systems, according to Patrick Worms, senior policy adviser at the World Agroforestry Centre.

The agriculture play seems a no-brainer given the macro statistics we constantly hear about. Over nine billion mouths to feed by 2050 on a planet increasingly buffeted by the disagreeable consequences of our collective environmental footprint.

What could go wrong? Plenty, as it turns out.

The most important is the deterioration of farmland through soil erosion, nutrient depletion, salinisation, land degradation and so on. These degrade food production and can eventually turn good farms into worthless wastelands. Agriculture can end up being economically similar to mining, an activity where a concession loses its value in proportion to the amount of minerals that have already been extracted.

Eventually, its worth can turn negative, when the environmental liabilities exceed the profits to be had from extracting whatever is left.

This process is neither new nor unique to modern farming. In his book Collapse, famed anthropologist Jared Diamond documents how civilisation after civilisation destroys itself through inappropriate agricultural practices.

Civilisational survival is not the rule. It is the exception.

Today, these dangers are widely recognised. And yet, most farmers – and most investors – continue to depend on production systems that expose them to avoidable long-term risks.

Take monocrop systems. While their many advantages explain their global prevalence, their inherent fragility is becoming increasingly clear as the costs of fertiliser and phytosanitation grow inexorably, droughts and storms damage exposed crops, and nutrients are lost through leaching and soil erosion.

Simple adaptations can help. Precision farming reduces environmental and financial downsides. Conservation agriculture protects the soil. But its dependence on herbicides brings other costs.

In the aggregate, such measures have failed to reverse adverse trends. The quality of farmland worldwide keeps dropping.

And yet alternatives exist. Farmers are experimenting with multicrop systems similar to those that have kept parts of the globe, such as China and Central America, densely populated for millennia.

Agroforestry is the most promising suite of such modernised systems. By adding trees to their fields, farmers gain a long list of benefits. Trees add organic carbon to the soil, protect it from erosion, help buffer storms and drought cycles, pump up nutrients from the deep soil and spread them via leaf litter, shade crops from excess sun, and host pest-eating creatures. And trees yield incomes from the sale of timber, pulpwood, fuelwood, fruits or nuts.

In agroforestry, the interactions between trees and crops play out to the benefit of both. Take cereals. Walnut roots must dig below meter-deep wheat roots before they can spread sideways, ensuring they are shielded from droughts. In a forest, tree roots are close to the surface, meaning fewer nutrients and more stress.  The walnut shade protects wheat from excess heat and raises its protein content. Trees continue exploiting sunlight and rainwater after the crop has been harvested.

The combined effect of these interactions is measured in one number, the Land Equivalency Ratio (LER) – the amount of land needed to generate the same return from segregated plots of crops and trees as from an agroforestry plot. Even in cold and overcast Britain, where competition for sunlight is intense, there are farms that achieve LERs of 1.4. In the tropics, LERs that exceed 3 are common.

Examples? A cereal farmer in the west of France, who planted 62 hectares of wheat/walnut agroforest 35 years ago, is generating a timber sale profit of two million euros after harvesting his usual cereal yield for most of the intervening period. In Brazil, we have an oil palm agroforestry plot that generates 60 percent more palm oil than local monocrop plantations, as well as cacao, banana, açai, maize and legumes from the same plot. And in Sumatra, modern rubber agroforestry generates over three times the revenue per hectare than rubber plantations do.

So why are these systems not spreading more rapidly? Three reasons. First, while they seem ancient, they are at the cutting edge of innovation. Unlike monocrop systems, they are rarely taught to agronomists. Farmers that want to use them are thus largely left to their own devices. It takes a stiff backbone to try something none of your neighbours is using, and about which finding advice is hard.

Second, they are more difficult to model. Spreadsheets can cope with the idea of a plantation producing one commodity, but one farm producing a continuously changing mix of commodities?

Third, their cost profile is not obvious. Take that oil palm. While labour costs are offset by much lower phytosanitation costs, they are higher than in monocrop systems, especially at the beginning. The system will, over its lifetime, generate a much better return of investment than a classic plantation, but plotting these complex returns over time is harder.

But agroforestry is spreading despite these challenges. Its unique productive and environmental profiles, and its integration into modern farming, are attractive. And the fact that agroforestry pretty much guarantees that the soil will be in a better condition at the end of the investment period than at its start doesn’t hurt.

Patrick Worms is the World Agroforestry Centre’s Senior Science Policy Adviser. He handles links between his research institution and investors out of his Waterloo, Belgium, office and can be contacted at p.worms@cgiar.org.