Biology:Bush encroachment

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bush encroachment at Waterberg Namibia
View of bush encroached land at the Waterberg Plateau Park in Otjozondjupa Region, Namibia

Bush encroachment is a natural phenomenon characterised by the excessive expansion of bush and shrub at the expense of other plant species, especially grasses. It is often considered an ecological regime shift. Bush encroachment is found to have severe negative consequences on key ecosystem services, especially biodiversity, animal habitat, land productivity and groundwater recharge. Bush encroachment can refer both to the expansion of native plants as well as the invasion and spread of invasive species. The phenomenon is observed across different ecosystems and with different characteristics and intensities globally. Among the more severely affected landscapes is the Veld in Southern Africa.

Causes

Various factors have been found to contribute to the process of bush encroachment. These include the reduction in the frequency of fires as well as overgrazing (e.g. caused by overstocking and fencing of farms). Another frequently cited theory is the state-and-transition model. This model outlines how rainfall and its variability is the key driver of vegetation growth and its composition. Further, climate change has been found to accelerate bush encroachment, as CO2 in the air fosters bush growth.[1][2]

Impact

Various ecosystem services are negatively impacted by bush encroachment, such as biodiversity, groundwater recharge and land productivity.

Biodiversity

Bush expands at the direct expense of other plant species, especially grasses. Moreover, various animal species are found to lose habitat in areas of bush encroachment, these include cats such as cheetah[3], antelopes such as the Common tsessebe and Hirola as well as birds such as the Secretarybird, Grey go-away-bird and the Kori bustard.

Bush Control

The term Bush Control refers to actions that are targeted at controlling the density and composition of bushes and shrubs in a given area that is affected by bush encroachment. Three different categories of measures can be distinguished:[4]

  • Responsive measures (bush thinning): the reduction of bush densities through targeted bush harvesting or other forms of removal.
  • Maintenance measures (aftercare): repeated or continuous measures of maintaining the bush density and composition that has been established through bush thinning.
  • Preventative measures (sustainable land management practices): application of proven good management practices to prevent the excessive growth of woody species, e.g. through appropriate stocking rates and rotational grazing in the case of rangeland agriculture.

Practices of combating bush encroachment, regardless of the exact methodology applied, are often referred to as "de-bushing". Although this term is widely used and also cited in various scientific works, it is disputed. "De-bushing" can easily be misunderstood as the practice of clearing and area of all bush plants, which is not the aim in most efforts to combat bush encroachment. The terms "bush control, "bush thinning" and "selective bush harvesting" are therefore considered more adequate terms.

Methods of bush control encompass natural bush control, mechanical bush control and chemical bush control. Natural bush control is among others achieved through the introduction of browsers, such as Boer goats.

Ecosystems affected by bush encroachment

Central Europe

Areas that formerly were forests require continuous maintenance to avoid bush encroachment. When active land cultivation ends, fallow land is the result and gradual spread of shrubs and bushes can follow. Animal species once native to Central Europe effectively countered this natural process. These include herbivores such as European bison, auerochs (extinct), red deer and feral horse. Grassland and heath are considered to require protection due to their biodiversity as well as to preserve cultural landscapes. Bush encroachment is therefore frequently countered with selective removal of woody biomass or through the seasonal or year-round introduction of grazing animal species. such as sheep, goats, heck cattle or horses.

Bush encroachment frequently occurs in the Alps, where structural change in the alpine agriculture often leads to the abandonment of land.

Southern African Savanna

Namibia

Causes and Extent

Various factors have been found to contribute to the process of bush encroachment. These include the reduction in the frequency of fires as well as overgrazing (e.g. caused by overstocking and fencing of farms). Another frequently cited theory is the state-and-transition model. This model outlines how rainfall and its variability is the key driver of vegetation growth and its composition. Further, climate change has been found to accelerate bush encroachment, as CO2 in the air fosters bush growth.

Bush encroachment is estimated to affect up to 45 million ha. Agricultural productivity in Namibia has declined by two thirds throughout the past decades, mainly due to the negative impact of bush encroachment. The phenomenon affects both commercial and communal farming in Namibia, mostly the central, eastern and north-eastern regions.[5]

Government response

The Government of Namibia has recognised bush encroachment as a key challenge for the national economy and food safety. In its current National Development Plan 5, it stipulates that a total of 82.200 ha of land shall be treated against bush encroachment annually, i.e. through the thinning of the bush density by means of selective bush harvesting[6] The Government of Namibia, through the Support to De-bushing Project, pursues a value addition strategy, promoting the sustainable utilisation of bush biomass, which in turn is expected to finance bush harvesting operations.

Beginning of 2014, a dedicated project to develop strategies and concepts for countering bush encroachment was launched in cooperation between the governments of Namibia and Germany, initially called Support to De-bushing Project. It is implemented jointly by the Namibian Ministry of Agriculture, Water and Forestry (MAWF) and the German development agency Deutsche Gesellschaft für Internationale Zusammenarbeit. Its first implementation phase ended in December 2017 and through bilateral negotiations the project was extended for a second phase, running between 2018 and 2021. The project was re-named to Bush Control and Biomass Utilisation Project to better reflect its strong emphasis on value chain development as trigger for sustainable bush control.

In 2019, the three Namibian farmers’ unions (NNFU, NAU/NLU, NECFU) together with the Ministry of Agriculture, Water and Forestry published a best strategy document called “Reviving Namibia’s Livestock Industry”.[7]

The documents states that the Namibian livestock industry is in decline due to the loss of palatable perennial grasses and the increase in bush encroachment. Namibia’s rangelands show higher levels of bare ground, lower levels of herbaceous cover, lower perennial grass cover, and higher bush densities over large areas. Bush thickening leads to direct competition for moisture with desirable forage species and detrimentally influences the health of the soil.

The best practice document identifies tried and tested practices of both emerging and established farmers from communal and title deed farms. These practices include the Split Ranch Approach, several Holistic Management approaches and the Mara Fodder Bank Approach. Other best practices include bush thinning, landscape rehydration and fodder production.

The unions state that there is major scope for enhancing livelihoods through the sustainable use of bush products. In addition, increased profitability and productivity of the sector will have a major impact on the 70% of the Namibian population that depends directly or indirectly on the rangeland resource for their economic well-being and food security.

Economic Activity

Increasingly, the encroaching bush is seen as a resource for a biomass industry. Economic assessments were conducted to quantify and value various key ecosystem services and land use options that are threatened by bush encroachment. The evaluation was part of the Economics of Land Degradation (ELD) Initiative,[8] a global initiative established in 2011 by the United Nations Convention to Combat Desertification, the German Federal Ministry for Economic Cooperation and Development, and the European Commission. Based on a national study, cost-benefit analysis suggests a programme of bush control to generate an estimated and aggregated potential net benefit of around N$48.0 billion (USD 3.8 billion) (2015 prices, discounted) over 25 years when compared with a scenario of no bush thinning. This implies a net benefit of around N$2 billion (USD 0.2 billion) (2015 prices, discounted) per annum in the initial round of 25 years.

The following products are currently produced from the encroacher bush biomass[9]:

  • Charcoal, mainly for export to South Africa and overseas markets (100.000 - 150.000 tonnes per annum)
  • Wood chips for energy applications, currently at the Ohorongo Cement factory and at Namibia Breweries Limited (estimated 40.000 tonnes per annum)
  • Wood briquettes mainly for private households, i.e. barbecuing or water heating
  • Bush based animal feed production, on experimental basis on various farms, especially in response to severe fodder shortages during periods of drought
  • Flooring/decking material, predominantly using Prosopis
  • Wood carvings

Namibia has a well-established charcoal sector, which currently comprises approximately 1.200 producers, which employ a total of 8.000 workers. Currently, most producers are farmers, who venture into charcoal production as a means to combat bush encroachment on their own land. However, increasingly small enterprises also venture into charcoal making. As per national forestry regulations, charcoal can only be produced from encroaching species. In practice, it however proves difficult to ensure full compliance with these regulations, as the charcoal production is highly decentralised and the inspection capacities of the Directorate of Forestry are low. Voluntary FSC certification has sharply increased in recent years, due to respective demand in many off-take countries, such as the United Kingdom, France and Germany. Due to exclusive use of encroacher bush for charcoal production, rendering the value chain free from deforestation, Namibian charcoal has been dubbed the "greenest charcoal" in an international comparison.[10]

Namibia Biomass Industry Group is a non-profit association under Section 21 of the Companies Act (Act 28 of 2004) of Namibia, founded in 2016. It functions as the umbrella representative body of the emerging bush based biomass sector in the country with voluntary paid membership. The core objectives, as enlisted in the Articles of Association, include to develop market opportunities for biomass from harvested encroacher bush as well as to address industry bottlenecks, such as skills shortages and research and development needs. The De-bushing Advisory Service is a division of the association, mandated with the dissemination of knowledge on the topics of bush encroachment, bush control and biomass utilisation. It was founded as a stand alone service in early 2016 with funding by the Government of Germany and later merged with Namibia Biomass Industry Group. It serves as a central knowledge and capacity development platform for the topic of bush control, facilitating sustainable large-scale bush control in Namibia. Its services therewith fall into the areas of rangeland management and natural resource management.[11] [12] Services are provided upon inquiry and are considered a public service and therefore not charged. According to its websites, services include technical advice on bush control and biomass utilisation, environmental advice, the strengthening of existing agricultural outreach services and linkage with service providers.

In August 2016 the Namibia Charcoal Association (NCA) emerged as a legal entity through a restructuring process of the Namibia Charcoal Producers Association, previously attached to Namibia Argicultural Union. It is a non-profit entity and the official industry representation, currently representing an estimated two-thirds of all charcoal producers in the country.

Environmental Regulations and Certification

Both the Forestry Act and the Environmental Act of Namibia govern bush control.

Effective April 2020 the Forest Stewardship Council introduced a national Namibian FSC standard (National Forest Stewardship Standard) that is closely aligned to the global FSC certification standard, but takes into consideration context specific parameters, such as bush encroachment.[13] In early 2020, the total land area certified under the FSC standard for the purpose of bush thinning and biomass processing was reported to amount to 1.6 million hectares.[14]

Botswana

Ecological surveys in Botswana have found bush encroachment affecting both communal grazing areas and private farmland, with particular prevalence in semi-arid ecosystems.[15][16][17] In selected areas, charcoal production has been introduced as a measure to reduce bush densities.[18][19][9]

South Africa

In South Africa bush encroachment entails the abundance of indigenous woody vegetation in grassland and savanna biomes. These biomes make up 27.9% and 32.5% of the land surface area. Research has found that about 7.3 million hectares are directly affected by bush encroachment.[20]

See also

Notes

References

  1. ↑ Tabares, X., Zimmermann, H., Dietze, E., Ratzmann, G., Belz, L., Vieth‐Hillebrand, A., Dupont, L., Wilkes, H., Mapani, B. and Herzschuh, U. (2020). "Vegetation state changes in the course of shrub encroachment in an African savanna since about 1850 CE and their potential drivers". Ecology and Evolution 10(2): 962-979. https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.5955. 
  2. ↑ Luvuno, L.; Biggs, R.; Stevens, N.; Esler, K. (2018). "Woody Encroachment as a Social-Ecological Regime Shift. Sustainability". Sustainability 10(7): 2221. https://www.mdpi.com/2071-1050/10/7/2221. 
  3. ↑ Nghikembua M., Marker L.L. Brewer, B., Mehtätalo, L., Appiah, M. and Pappinen, A. (October 2020). "Response of wildlife to bush thinning on the north central freehold farmlands of Namibia". Forest Ecology and Management Volume 473, 1. https://www.sciencedirect.com/science/article/abs/pii/S0378112720310999. 
  4. ↑ http://www.dasnamibia.org/wp-content/uploads/2016/07/De-Klerk-Bush-Encoachment-in-Namibia-2004.pdf
  5. ↑ "Bush encroachment must be curbed". Namibia Economist. https://economist.com.na/13437/environment/bush-encroachment-must-be-curbed/. Retrieved 23 October 2015. 
  6. ↑ http://www.gov.na/documents/10181/14226/NDP+5/5a0620ab-4f8f-4606-a449-ea0c810898cc?version=1.0
  7. ↑ "Reviving Namibia's Livestock Industry". http://www.agrinamibia.com.na/wp-content/uploads/2019/10/NRMPS-Revised-Strategy-2019-Rangeland-Best-Practices-final.pdf. 
  8. ↑ https://www.eld-initiative.org/fileadmin/pdf/Namibia_PolicyBrief.pdf
  9. ↑ 9.0 9.1 Charis, G., Danha, G., and Muzenda, E. (2019). "Waste valorisation opportunities for bush encroacher biomass in savannah ecosystems: A comparative case analysis of Botswana and Namibia". Procedia Manufacturing Volume 35: 974-979. https://www.sciencedirect.com/science/article/pii/S2351978919307693. 
  10. ↑ FSC Africa (2020-03-17). "From Bush to Charcoal: the Greenest Charcoal Comes from Namibia". https://fsc.org/en/newsfeed/from-bush-to-charcoal-the-greenest-charcoal-comes-from-namibia. 
  11. ↑ Hoffmann, Jürgen. "De-bushing initiatives are coordinated". South African Institute of International Affairs. https://www.newera.com.na/2015/02/24/de-bushing-initiatives-coordinated/. Retrieved 24 February 2015. 
  12. ↑ Shigwedha, Absalom. "De-bushing advisory service set up". The Namibian. http://www.namibian.com.na/155549/archive-read/De-bushing-advisory-service-set-up. Retrieved 13 November 2016. 
  13. ↑ "The FSC National Forest Stewardship Standard for the Republic of Namibia". FSC International. https://fsc.org/en/document-centre/documents/resource/418. Retrieved 17 February 2020. 
  14. ↑ FSC Africa (2020-04-10). "1,6 million hectares: Namibia reaches new heights in FSC certification". https://africa.fsc.org/en-cd/actualits/press-releases/id/364. 
  15. ↑ Dougill, Andrew J. (2016-02-09). "Land use, rangeland degradation and ecological changes in the southern Kalahari, Botswana". African Journal of Ecology Volume 54, Issue 1: 9. https://www.researchgate.net/publication/293805521_Land_use_rangeland_degradation_and_ecological_changes_in_the_southern_Kalahari_Botswana. 
  16. ↑ Kgosikoma, O. E. (2012-02-27). "Bush encroachment in relation to rangeland management systems and environmental conditions in Kalahari ecosystem of Botswana". African Journal of Agricultural Research Vol. 7(15), pp. 2312-2319: 8. https://www.researchgate.net/publication/260984138_Bush_encroachment_in_relation_to_rangeland_management_systems_and_environmental_conditions_in_Kalahari_ecosystem_of_Botswana. 
  17. ↑ Ringrose, Susan (1996-07-01). "The use of integrated remotely sensed and GIS data to determine causes of vegetation cover change in southern Botswana". Applied Geography Volume 16, Issue 3: Pages 225-242. https://www.sciencedirect.com/science/article/abs/pii/0143622896000057. 
  18. ↑ Mmolai, Esther (2018-01-23). "Botswana: Savannah Degradation Threatens Country". AllAfrica. https://allafrica.com/stories/201801240243.html. 
  19. ↑ Keakabetse, Boniface (2017-12-05). "North-West communities pilot climate smart projects". Mmegi Online. http://www.mmegi.bw/index.php?aid=73490&dir=2017/december/0. 
  20. ↑ Department of Environmental Affairs (2019). Towards a Policy on Indigenous Bush Encroachment in South Africa. https://www.environment.gov.za/sites/default/files/reports/indigenousbushencroachment_policybrief.pdf. 

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External links



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