Wind can have a devastating impact on in dry areas. It blows away the top layer of soil, with disastrous consequences for soil fertility and food production. It damages equipment and infrastructure. Moreover, soil particles mixed with chemical substances and pesticides pose a human health risk. But something can be done about this, says Syrian Feras Youssef in his PhD thesis on the effects of vegetation on wind erosion on a regional scale. Since plants and shrubs break the force of the wind, clever planting can prevent wind erosion and even restore degraded land. But what constitutes ‘clever’? In other words, what is the most suitable pattern for planting? To find out, Youssef studied the effects of various planting patterns in a special wind tunnel at Ghent University.
Sand catchers
There is no uniform answer. ‘It depends on what you want to achieve,’ explains Youssef. Each pattern has its own advantages. Plants in straight lines parallel to the wind direction will result in the smallest amount of sand being transported, his measurements show. But sand can travel far along this kind of ‘street’ of shrubs. Other planting patterns stop sand from being transported so far, but the amount of sand transported is higher. So it all depends on what you want. Youssef also took field measurements in Syrian. Using sand catchers, he charted the erosion in an entire region. This has not been done on such a scale before. ‘Measurements are usually taken for a particular land usage. I studied an entire region which has various forms of land-use. This gives a much more realistic picture of erosion than when you extrapolate from just one little area.’ Using the data collected in the field and from the wind tunnel, Youssef developed a model which can predict wind erosion on a regional scale for different types of vegetation. Policy makers and landscape managers can use it to combat erosion in a targeted fashion. ‘If you want to diagnose a problem or draw up measures based on a policy, you will want to know what happens in a region instead of on a small plot of land.’