We often talk about the importance of eliminating alien vegetation in the Waterberg and beyond. Here below is my edited version of an article in Science and Development Network about a very technical study published in Ecology Letters.
Following that is an interesting exchange, also edited, from Mozambique on the subject. Marcos Freire is the Research Coordinator for the Farmer Income Support Project in Zambézia Province, Mozambique. Jake Walter is TechnoServe's Country Director in Mozambique. Chuck Stephens, the Programme Director for Tearfund, is based now in Juba, South Sudan.
Edited version of Alien plants 'can help alleviate poverty': Alien plant species can significantly reduce biodiversity but they can also boost an ecosystem's biomass production. Introduced alien species are usually seen as a threat to biodiversity and hence to the poor who depend on ecosystems for their livelihoods. But boosting the amount of biomass produced is seen by some as more important for alleviating poverty than conserving biodiversity. "For the rural poor who depend on what nature provides, volume matters more than the variety ... Increasing the volume of biomass nature produces is crucial for alleviating poverty." says Craig Leisher, senior social-science advisor at the US-based Nature Conservancy.
Now there is evidence that invasive plant species may help boost the overall plant volume produced in the ecosystems they are introduced into. Alien species are often introduced to fill empty niches, reduce soil erosion and increase food production especially in developing countries. Examples of introduced species that boost biomass production include Eucalyptus and Pinus tree species in South Africa, where the latter are now spreading through the native ecosystems. Leisher said that we may sometimes have to sacrifice biodiversity to feed a growing population.
"It's not pragmatic to try and save all the species on the planet, at any cost. The surest way to provide long-term protection for nature is empowering communities to co-manage their natural areas to sustainably produce the things they value, such as fish, fuel, fodder and clean water." Jake Walter: I agree that the potential is substantial for planted trees of alien species, including eucalyptus, in Mozambique. It will have a very large positive economic and environmental impact. Of course, they would not be the first alien plants grown widely in Mozambique. Maize and cassava, the most widely grown plants – not to mention cashew trees, which originated in Brazil – are also alien plants, as well as groundnuts, which originated in Bolivia. Marcos Freire: Properly managed forests planted to alien/exotic species can be beneficial both for the owner and "the country" in general.
The main issue is one of balancing ownership (who owns the resource?), who benefits from the resource (who gets the profits? is it distributed to the local communities? or is it just a way of using local soil resources?), does the country as a whole really benefit from it (are we just producing raw materials? or do we process it?). In many cases these planted forests are just harvested for exporting raw materials, in which case it is usually a way of using a local resource, paying a few people minimum wage, and exporting a cheap product that will bring minimal benefits to the country. With crops it is a bit different as most are used one way or another for direct consumption. Actually the quantity of "alien/exotic" species being used in Mozambique is huge. Let's say that, apart from cowpea most other crops (annual and perennial, fruits included) are "alien".
Continuing with Jake's list: maize, rice, wheat, cotton, sesame, sunflower, groundnuts, beans, most vegetables, potatoes, sugarcane, all citrus, mangoes, cashew, coconuts, ... do you really want to continue... Jake Walter: FAO estimates that in addition to protecting over a million hectares of forest/wildlife land, the plantation forestry industry will employ between 300,000 and 500,000 people, making it the largest employer in the country; and mostly rural employment, which the country especially needs.
Chuck Stephens: If you visit the Arboretum in Sussundenga, Mozambique, you will find that there are various indigenous species of trees that out-grow gum trees by a long shot, in terms of cubic meters per year, without consuming so much ground water. Let's face it, gum trees were used in Australia to drain swamps. In South Africa, it is illegal to plant gum trees within a minimum distance of creeks – they just dry them up. Southern Africa has to take the water emergency more seriously. I agree that poor people need to see output and that Europeans don't eat chestnuts any more – like they used to before potatoes were brought from the New World. But with climate change, southern Africa is already up for desertification – let's not accelerate it by planting gum trees.