Green Invasion: Destroying Livelihoods in Africa [Video]

CABI, together with Tmax Productions, have produced a video called the ‘Green Invasion – Destroying Livelihoods in Africa.” The short film (approx. 7mins long) details how invasive weeds are impacting on the lives of rural communities in East Africa.

Although a large number of non-native species have become invasive in the region, this film focusses on four of the most problematic species namely Chromolaena odorata (Devil weed), Parthenium hysterophorus (famine weed), Prosopis juliflora (Mathenge) and Opuntia stricta (erect prickly pear). The excellent footage shows the extent of  weed infestations with accounts from community members on how these invasive plants are destroying the natural resource base on which they depend. It is clear that invasive weeds are destroying traditions, cultures and a way of life for millions of people on the continent.

However, all is not lost. The film notes that if effective management programmes are implemented, including biological control, we can make a difference to many people’s lives.

Although of general interest, the film is intended to raise the profile of invasive species and their impacts on livelihoods amongst donors and governments. We need them to take action and provide support for initiatives to manage one of the biggest threats to economic development on the planet.

Arne Witt
CABI Regional Coordinator, Invasives (Africa & Asia)
@WittArne


Use them and lose

Is promoting the utilisation of invasive non-native species for commercial or other uses e.g. as a feed for livestock, use as a fuel or to produce biogas, a help or a hindrance to their control?

A view from Arne Witt, CABI Regional Coordinator, Invasives (Africa & Asia):

Promoting the utilization of any invasive non-native species (INNS) has largely contributed to their spread, especially in most developing countries which don’t have the capacity to develop and implement effective integrated management strategies.  Utilization as a control can only be effective if it forms part of an integrated management plan – on its own it merely exacerbates the problem.  There are many examples of where INNS have been intentionally spread by individuals because they have been led to believe that they can enrich themselves by growing and then utilizing an INNS – at low densities many INNS are beneficial, but it does not stay that way for very long – short-term benefits but long-term costs.

One needs to remember that utilization works from “inside out” whereas “control or management” works from “outside-in”.  In other words, the most cost-effective way to utilize an INNS is at the largest and densest infestations. As such you would build your biogas plant or sawmill in an area where the costs with regard to transport are lowest. In addition, you would not “eradicate” any of the plants you utilize – it is expensive and time-consuming to do so and why would you want to anyway, you want a renewable resource, so getting the plants to coppice, so that you can use them again in the future, is exactly what you want.  This is largely what is happening in Africa – those utilizing prosopis for charcoal do not apply herbicide to the cut stumps or dig out the rootstock – they want the plants to coppice. The same happens in India with regard to the utilization of lantana – communities don’t kill the lantana, they allow it to coppice. In addition, it does not make economic sense to utilize plants growing individually or in small pockets away from these dense infestations, especially in developing countries where we have poor infrastructure.  For a control/management strategy to be effective we need to work from the “outside-in”, removing individual plants or small isolated stands first before moving onto the dense stands – utilization works in the opposite way which is why it is ineffective as a management strategy on its own.

African landscape dominated by prosopis

African landscape dominated by prosopis (Arne Witt, CABI)

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The value of costing nature in the fight against invasive species

Increasingly we are seeing the terms ‘ecosystem services’, ‘ecosystem functioning’ and ‘ecosystem processes’ in the media and the scientific literature, to highlight the benefits the natural environment provides to our wellbeing.  Invasive species, from bivalves to balsams, have the potential to impact on ecosystem services, though it is widely accepted that there are gaps in our understanding within this field.

Ecosystem services can be defined as the ecosystem processes that we as humans benefit from and they can be categorised into four groups:

Provisioning: The ecosystem provides products essential for our everyday needs including timber, fuel, food, genetic resources and medicine.

Regulating: We gain from natural services including pollination of wild plants and crops by bees, by rivers and floodplains providing natural flood management, and climatic regulation.

Cultural: We benefit from natural spaces for recreation and social activity.  We find harmony in natural areas that are aesthetically pleasing.

Supporting: These services underpin all of those mentioned above.  Biological diversity promotes stability and a healthy ecosystem, nutrient acquisition and flow through the ecosystem by fungal and invertebrate decomposers, and primary production.

American Beaver, Castor canadensis - Steve Hersey, Flickr

The north American beaver, Castor canadensis has had a catastrophic impact on Chile’s sub-Antarctic forests impacting on provisional services
Photo: Steve Hersey, Flickr

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