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| | Invasive alien species cause economic, social and environmental damage and pose a threat to natural ecosystems and agroecosystems as well. Their impact runs through various issues of global interest such as food security, sustainable resource management and preservation of biodiversity. The most cost-efficient method for intervention is prevention though it requires cooperation on national and international level. | | Invasive alien species cause economic, social and environmental damage and pose a threat to natural ecosystems and agroecosystems as well. Their impact runs through various issues of global interest such as food security, sustainable resource management and preservation of biodiversity. The most cost-efficient method for intervention is prevention though it requires cooperation on national and international level. |
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| − | [[Ethiopia-National Plan for Prosopis-3 February 2002|Ethiopia-National Plan for Prosopis]]
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| − | [[The Ecological and Socio-economic Role of Prosopis juliflora in Eritrea|The Ecological and Socio-economic Role of Prosopis juliflora in Eritrea]] | + | [[Ethiopia-National Plan for Prosopis-3 February 2002|Felker, P. (2002), Ethiopia-National Plan for Prosopis]] |
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| − | [[Management, Use and Control of Prosopis in Yemen|Management, Use and Control of Prosopis in Yemen]] | + | [[The Ecological and Socio-economic Role of Prosopis juliflora in Eritrea|Bokrezion, H. (2008), The Ecological and Socio-economic Role of Prosopis juliflora in Eritrea]] |
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| | + | [[Management, Use and Control of Prosopis in Yemen|Felker, P. (2003), Management, Use and Control of Prosopis in Yemen]] |
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| | + | [[The human dimensions of invasive|Binggelli, P. (2001), The human dimensions of invasive woody plants]] |
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Revision as of 16:11, 9 December 2014
Introduction
A species is considered an “alien invasive species” when it spreads beyond its natural area of distribution and moreover causes harm or is likely to cause harm to the environment, people, economy or human health.
In economic terms, the costs of invasive alien species are significant. Total annual costs include losses to crops, pastures, livestock, water and forests, as well as environmental damages. These costs have been estimated to be in the hundreds of billions of dollars and possibly more than one trillion. This does not include other values like losses in biodiversity or ecosystem services (Pimentel et al., 2001).
Spreading
The movement of organisms from one ecosystem to another expanded mainly due to increased global trade, transport and tourism. Goods traded by land, water or air may contain living plants and animals or their eggs and spores. The major vessel for aquatic organisms is the national and international trade by ships which can carry organisms in their ballast water. In other cases foreign species are introduced on purpose, such as crops, pets, ornamentals or game. Moreover in some cases species are imposed to deal with environmental issues, for example Prosopis juliflora (Link) to combat erosion and desertification in the Horn of Africa (FAO). Movements of species are also driven by climate change that either forces organisms to move north or facilitates formerly blocked ways for others.
Impact
Whereas many organisms introduced into new environments cannot survive in their new surrounding others distribute successfully. They may even displace native species. This mainly happens in two ways: Either the invasive species actively suppresses or excludes natives by lowering resource availability to levels that only they can tolerate (Tilman, 1988) or the invasive species is largely unaffected by recruitment barriers or environmental stressors that are highly limiting to other species (Grime, 2001). Due to the displacement of native species major transformations in the local ecosystem can be provoked. Besides habitat alteration, invasive alien species impacts have been a cause for the extinctions of species over the past few hundred years. Although in the past, many of these losses have gone unrecorded, today, there is an increasing realisation of the ecological costs of biological invasion in terms of irretrievable loss of native biodiversity and degradation of ecosystem functioning (http://www.issg.org/about_is.htm ). Furthermore, the new arrival of certain species into new territories may have detrimental effects on human health as well. Such negative effects occur when the invasive species is a pathogen itself or is a vector for pathogens or if it changes an ecosystem in such a way that pathogens can better thrive (Neill and Arim, 2011).
Examples
Soil
Loss in natural vegetation may lead to a loss in soil organic matter (SOM) and a loss in soil stability. In Rajasthan, India, grazing areas are shrinking and degrading as native grass species (Dicanthium – Chenchrus – Lasiurus species) become replaced by ephemeral grasses (Eragrostis and Aristida fumiculata), which are both less palatable and less yielding. Due to this, overgrazing has increased and causes further degradation (Venkateswarlu, 2012).
Water
In the American West, the Salt Cedar, that was introduced as an ornamental plant, lowers the ground water table due to its immense water consumption. A single large plant can absorb 200 gallons of water a day (Hoddenbach 1987). It out-competes native riparian plants, such as willows and cottonwoods (Sudbrock 1993) and can also dry up springs and marshy areas. Paradoxically, Salt Cedar infestations can also lead to flooding, as its extensive root system can choke stream beds (Rush 1994).
Food Security
Newly introduced organisms may have a negative influence on yields. In Uganda and Mozambique the groundnut minor (Aproaerema modicella ) is an invasive alien Asian species. When first reported in the region in 1998 it caused high yield losses and withdrawal from groundnut farming in the southern regions and by this it poses an example as a threat to food security in the area (Cuagala et al. 2010).
Intervention
To intervene in the spreading of alien invasive species there are mainly three approaches: prevention, eradiction/ control and restoration.
Prevention
As preventing international movements and fast detection of alien invasive species are less costly than control and eradication, there are many agreements that include regulations on invasive species (e.g. Agenda 21, Global Programme of Action for the Protection of the Marine Environment from Land-based Activities (GPA)). Prevention includes inspection of ships and other transport vessels as well as quarantine regulations. These can be conducted either for individual species or for whole pathways. Whereas these regulations must be implemented by national and international governments, it is also crucial to inform the general public in order to enable them to make responsible decisions.
Eradication/ Control
Eradication programmes aim towards the fast and complete extinction of alien invasive species, whereas control programmes are designed for long-term management. Eradication is best feasible for mammals and on islands whereas plants and insects are more challenging. The methods for eradication and control as well include the use of toxins, shooting, mechanical removal and trapping. However many of these measures are expensive bare their own risks. Therefore not every method will fit for every region or problem. Aside from good planning, gaining support from local people is often necessary for a successful programme.
Restoration
For complete restoration of a harmed area replanting of native flora and reintroduction of fauna is frequently necessary. Once an area is restored, prevention is also required to keep an invasive species from returning.
Conclusion
Invasive alien species cause economic, social and environmental damage and pose a threat to natural ecosystems and agroecosystems as well. Their impact runs through various issues of global interest such as food security, sustainable resource management and preservation of biodiversity. The most cost-efficient method for intervention is prevention though it requires cooperation on national and international level.
Furthr Reading
Felker, P. (2002), Ethiopia-National Plan for Prosopis
Bokrezion, H. (2008), The Ecological and Socio-economic Role of Prosopis juliflora in Eritrea
Felker, P. (2003), Management, Use and Control of Prosopis in Yemen
Binggelli, P. (2001), The human dimensions of invasive woody plants
References
Grime, J. P. 2001. Plant strategies, vegetation processes, and ecosystem properties. John Wiley and Sons, Chichester, UK.
Tilman, D. 1988. Plant strategies and the dynamics and structure of plant communities. Princeton University Press, Princeton, New Jersey, USA.
Venkateswarlu, J. 2012. Loss in biodiversity with desertification in Arid Rajasthan. LEISA INDIA. Volume 14 no. 4
Cugala, D., Santos, L., Botao, M., Solomone, A., Sidumo, A. 2010. Assessment of groundnut yield loss due to the groundnut leaf miner, Aproaerema modicella infestation in Mozambique. Second RUFORUM Biennial Meeting. Maputo, Mozambique
Hoddenbach, G. 1987. Tamarix control. Tamarisk control in southwestern United States. Cooperative National Park Resources Studies Unit, Special Report No. 9: 116-125.
Rush, E. 1994. Strangers in the wilderness. Pacific Horticulture 55: 20-23.
Neill, P. and Arim, M. 2011. 'Human Health Link to Invasive Species'. In Nriagu, J (ed) Encyclopedia of Environmental Health. Elsevier, Oxford, UK.
Pimentel, D., S. McNair, J. Janecka, J. Wightman, C. Simmonds, C. O’Connell, E. Wong, L. Russel, J. Zern, T. Aquino, T. Tsomondo 2001. Economic and environmental threats of alien plant, animal, and microbe invasions. Agriculture, Ecosystems and Environment 84 (2001) 1–20.
Sudbrock, A. 1993. Tamarisk control. I. Fighting Back: An overview of the invasion, and a low-impact way of fighting it. Restoration and Management Notes 11: 31-34.
http://www.issg.org/about_is.html
http://www.fao.org/docrep/006/ad317e/AD317E02.html
http://www.fao.org/docrep/006/ad317e/AD317E02.html
Regional Conference on Managing Prosopis Juliflora
Regional Conference on Managing Prosopis Juliflora for better (agro-)pastoral Livelihoods in the Horn of Africa
Conference Date: May 1 - May 2, 2014
Location: Desalegn Hotel, Addis Ababa, Ethiopia
Prosopis juliflora is one of the world’s worst invasive alien species and threatens the ASAL areas in the Horn of Africa with environmental degradation. Many countries such as Ethiopia, Sudan, Djibouti, Kenya, Eritrea, and Somalia are heavily affected by the prosopis invasion. In Ethiopia’s Afar Region a tremendous land mass of more than 1,2 Mio. ha has already been invaded with an alarming expanding rate per year as prosopis rapidly spreads across both pastoral and agricultural lands. Also in other areas such as Kenya’s Turkana and Marsabit County, prosopis is a major driver of degradation, leading to severe losses in land and ecological functions, and challenges (agro-)pastoral livelihoods and food security in the region.
On behalf of the German Federal Ministry for Economic Cooperation and Development (BMZ), GIZ, Mekele University, and UNESCO-IHE held a regional conference on prosopis juliflora for the Horn of Africa. The conference brought together prosopis researchers and academics from various backgrounds, policy makers, practitioners, and development agents to learn about the background, impacts and drivers of prosopis invasion in the region, share knowledge and experiences on prosopis eradication and management, and discuss how prosopis can be better managed in the future to reduce degradation and to strengthen (agro-)pastoral livelihoods and food security.
The following link gives access to the conference presentations:
[[1]]
http://thewaterchannel.tv/media-gallery/5870-prosopis-juliflora-in-afar-ethiopia-english
