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Desertification

Desertification is the degradation of drylands which include arid, semi-arid and sub-humid areas. Drylands make up roughly 40 percent of the Earth’s land and are home to some two billion people, most of which live in developing countries. Dryland soil sustains a fragile ecosystem adapted to infrequent precipitation and dramatic temperature changes. Over-exploitation of dryland for cultivation and feedstock purposes renders the soil unproductive, forcing migration of communities in search of fertile land, leaving the unproductive land bare and vulnerable to erosive forces. A lack of food supply in many developing countries forces constant cultivation of land for short-term gain as well as deforestation to provide arable land.

Engineering bacteria to help fight soil erosion

In arid areas of the world soil erosion is a massive problem. It is caused by wind and rain sweeping away the fertile top soil and can eventually result in desertification.

Climate change and unsustainable farming practices are accelerating the rate of desertification to over 31,000 hectares/day. That’s 62, 000 football pitches in a day or half the size of the UK every year.

In ordinary circumstances the roots of well-established plants help to hold down the top soil, protecting it from erosion. In areas that suffer desertification however plants do not get the chance to establish large enough root networks to anchor the soil and themselves before erosion occurs.

This year, Imperial College’s iGEM team have joined the international effort to fight desertification.

We hope to engineer bacteria to accelerate plant root development. The bacteria will be designed to secrete the hormone auxin. Seeds will be coated with the bacteria and then planted in the soil. Once the seeds germinate the bacteria will move towards the roots and be taken in by the plant. Inside the roots the bacteria will release auxin – promoting growth and protecting the soil from erosion.

Case Studies

Desertification

Mouse over the map to read about the impact of desertification in different areas.

Downstream Effects

Soil affects the climate and biodiversity and leads to often irreversible desertification (see figure above). Roots increase the stability of soil and prevent erosion (Gyssels & Poesen, 2003). In addition, trees provide cover and protect nearby fauna and flora. In areas prone to soil erosion, this is especially important as rainfall tends to be rare but when it does occur, it is often very intense and easily leads to topsoil being washed away. Roots are also important carbon sinks. Increasing root biomass is therefore very likely to improve the carbon budget of the plants we are seeding (Dr Alexandru Milcu, oral communication).

UN, Ecosystems and human well-being - Desertification synthesis.