Soils bleeding to death
I remember the first time I saw a satellite image of Jamaica viewed from outer space. The waters east of Morant Point were clear and blue, but to the west of Negril Point, heading towards the Yucatan, was a brown plume of silt being carried in the current. "Jamaica is washing away!" I said to myself.
Indeed! It is estimated that each year, we lose more than 80 million tons of topsoil, much of it ending up in the Caribbean Sea. Dig anywhere in Jamaica and pretty soon you reach the subsoil - geological material which cannot support agriculture. Only the thin layer of topsoil on the surface is available for food production, and every year, we have less and less of it. Since Independence, we have lost a staggering 4.2 billion tons of topsoil. Jamaica is bleeding to death!
Our agricultural production is in decline because of a number of factors, including unfair competition from subsidised imports. But of greater concern is the fact that the productivity of our land is declining. Each year, the same acre of land produces less and less output. Drought and storms are usually blamed for this, and they do play a role, but a factor we often ignore is topsoil depletion. Each year, we have less topsoil with which to feed ourselves. It doesn't take a rocket scientist to calculate what lies ahead.
NOT JUST DIRT
Topsoil is not just dirt. It contains minerals in small quantities (micro-nutrients) that are essential components for the healthy functioning of our bodies. Healthy topsoil also contains microorganisms which assist plant growth. Degrading the topsoil and killing the microorganisms also kill the soil, making it less fit for agriculture.
The United Nations (UN) estimates that to keep up with increasing global food demand, six million hectares (14.8 million acres) of new farmland will be needed every year. Instead, 12 million hectares are lost each year through soil degradation. We wreck it, then move on, trashing rainforests and other precious habitats as we go. Soil is a living system, yet we treat it like, well, dirt.
Jamaica is not the only country with this problem; it is a global issue. On December 20, 2013, the 68th session of the UN General Assembly declared December 5 every year to be World Soil Day, and 2015 to be the International Year of Soils to raise worldwide awareness of the importance of soils for food security and agriculture, as well as in mitigation of climate change, poverty alleviation, and sustainable development.
Tomorrow - the second-ever World Soil Day - will bring the International Year of Soils to a close, and despite Jamaica's massive problem of soil depletion, I can't say that awareness of the problem and the possible solutions have much increased.
Trees hold the soil with their roots and prevent erosion. Leaves on the ground take the full force of raindrops falling with great energy from great height. Without trees and their litterfall, with every shower of rain, the soil washes away into streams and rivers, which will run brown with topsoil (what we call in Jamaica "river come down"), and then into the sea.
LITTLE FOREST LEFT
Deforestation is the major cause of soil erosion, and some time not too long ago, Jamaica was ranked as having the highest rate of deforestation in the world. We can't win that prize again because we have so little forest left.
The way we do mining requires every tree and blade of grass to be stripped away before we start digging. Before we plant coffee or timber trees in the mountains, we clear away the natural forest cover down to the bare earth - sometimes by fire. And when the topsoil washes away, we wonder why the yield is so low. Or we use the same plot of land year after year (say, for growing sugar or bananas), depleting the mineral nutrients and organic matter. Our agricultural methods convert healthy land into desert.
Either we avoid the use of inorganic fertiliser, or we utilise it inappropriately. Studies show that without adequate soil carbon and organic matter, plants absorb fewer of the nutrients in inorganic fertilisers. The effect of inorganic fertilisers on crop yields are far greater when applied to healthy soils with higher levels of soil carbon and organic matter, than when applied to degraded soils. Since poorer farmers most commonly cultivate the most degraded soils, fertiliser policies aimed at helping the poor may actually reinforce income inequalities.
Using manure rather than inorganic fertiliser, or running livestock in the fields between plantings, may give better results.
We have been treating our soils like dirt, and we are paying the price for it.
- Peter Espeut is a sociologist and rural development scientist. Email feedback to firstname.lastname@example.org.