SUNScholar - Browsing by Author "Shackleton, Ross T."

Browsing by Author "Shackleton, Ross T."

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Distribution and socio-ecological impacts of the invasive alien cactus Opuntia stricta in Eastern Africa
(Springer, 2017-05-13) Shackleton, Ross T.; Witt, Arne B. R.; Piroris, Francis M.; Van Wilgen, Brian W.
ENGLISH ABSTRACT: Many cactus species have been introduced around the world and have subsequently become major invaders, inducing social and ecological costs. We recorded the distribution of Opuntia stricta in eastern Africa, and conducted 200 household interviews using semi-structured questionnaires to assess local perceptions of O. stricta in Laikipia County, Kenya. Opuntia stricta was widespread and abundant in parts of Kenya, Tanzania and Ethiopia and present at low densities in Uganda. In Laikipia County, pastoralists identified that O. stricta had been present for more than 10 years, and were of the opinion that it was still spreading and increasing in density. Two-thirds of respondents estimated that 50–75% of valuable grazing land had been invaded, and all felt that it contributed to the ill-health and death of livestock. Other negative impacts included reductions in native plant populations, rangeland condition, human health, and mobility of humans and animals. These negative impacts resulted in economic losses of US$ 500–1000 per household per year for 48% of households. Only 20% of respondents reported actively managing O. stricta, yet all respondents believed a reduction in the abundance of this weed would improve well-being. Management interventions are needed to reduce negative impacts.
Distribution of invasive alien Tithonia (Asteraceae) species in eastern and southern Africa and the socioecological impacts of T. diversifolia in Zambia
(South African National Biodiversity Institute (SANBI), 2019-09-25) Witt, Arne B.R.; Shackleton, Ross T.; Beale, Tim; Nunda, Winnie; Van Wilgen, Brian W.
Background: Many alien plant species, such as Tithonia diversifolia, T. rotundifolia and T. tubaeformis, have been introduced to areas outside of their natural distribution range to provide benefits, but have subsequently become invasive, threatening biodiversity and agricultural productivity. Objectives: The aim of this study was to determine the current distribution and dates of introduction of invasive Tithonia species in eastern and southern Africa and to document the effects of T. diversifolia on rural livelihoods in Zambia. Method: Roadside surveys, and other sources of information, were used to determine the distribution of invasive Tithonia species in eastern and southern Africa. Household interviews were conducted to gauge perceptions and understand the impacts of T. diversifolia on local livelihoods in Zambia’s Copperbelt province. Results: Tithonia diversifolia is widespread in Uganda, Kenya, Tanzania, South Africa, Malawi and parts of Zambia but less so in Zimbabwe. Tithonia rotundifolia was comparatively uncommon in eastern Africa but common in some southern African countries, while T. tubaeformis was invasive in Swaziland, South Africa, Zambia and possibly also Zimbabwe. According to the majority of respondents in Zambia, T. diversifolia has negative impacts on native vegetation, mobility or access, water availability, crop yields and animal health. Conclusion: Invasive Tithonia species are widespread and spreading throughout much of Africa. Livelihood and biodiversity costs have not been considered by those actively promoting the use and further dissemination of T. diversifolia. We therefore recommend that detailed cost–benefit studies should be undertaken to support informed decisions on the future management of these species.
Global effects of non-native tree species on multiple ecosystem services
(Wiley, 2019-04-19) Castro-Diez, Pilar; Vaz, Ana Sofia; Silva, Joaquim S.; Van Loo, Marcela; Alonso, Alvaro; Aponte, Cristina; Bayon, Alvaro; Bellingham, Peter J.; Chiuffo, Mariana C.; DiManno, Nicole; Julian, Kahua; Kandert, Susanne; La Porta, Nicola; Marchante, Helia; Maule, Hamish G.; Mayfield, Margaret M.; Metcalfe, Daniel; Monteverdi, M. Cristina; Nunez, Martin A.; Ostertag, Rebecca; Parker, Ingrid M.; Peltzer, Duane A.; Potgieter, Luke J.; Raymundo, Maia; Rayome, Donald; Reisman-Berman, Orna; Richardson, David M.; Roos, Ruben E.; Saldana, Asuncion; Shackleton, Ross T.; Torres, Agostina; Trudgen, Melinda; Urban, Josef; Vicente, Joana R.; Vila, Montserrat; Ylioja, Tiina; Zenni, Rafael D.; Godoy, Oscar
Non-native tree (NNT) species have been transported worldwide to create or enhance services that are fundamental for human well-being, such as timber provision, erosion control or ornamental value; yet NNTs can also produce undesired effects, such as fire proneness or pollen allergenicity. Despite the variety of effects that NNTs have on multiple ecosystem services, a global quantitative assessment of their costs and benefits is still lacking. Such information is critical for decision-making, management and sustainable exploitation of NNTs. We present here a global assessment of NNT effects on the three main categories of ecosystem services, including regulating (RES), provisioning (PES) and cultural services (CES), and on an ecosystem disservice (EDS), i.e. pollen allergenicity. By searching the scientific literature, country forestry reports, and social media, we compiled a global data set of 1683 case studies from over 125 NNT species, covering 44 countries, all continents but Antarctica, and seven biomes. Using differentmeta-analysis techniques, we found that, while NNTs increase most RES (e.g. climate regulation, soil erosion control, fertility and formation), they decrease PES (e.g. NNTs contribute less than native trees to global timber provision). Also, they have different effects on CES (e.g. increase aesthetic values but decrease scientific interest), and no effect on the EDS considered. NNT effects on each ecosystem (dis)service showed a strong context dependency, varying across NNT types, biomes and socio-economic conditions. For instance, some RES are increased more by NNTs able to fix atmospheric nitrogen, and when the ecosystem is located in low-latitude biomes; some CES are increased more by NNTs in less-wealthy countries or in countries with higher gross domestic products. The effects of NNTs on several ecosystem (dis)services exhibited some synergies (e.g. among soil fertility, soil formation and climate regulation or between aesthetic values and pollen allergenicity), but also trade-offs (e.g. between fire regulation and soil erosion control). Our analyses provide a quantitative understanding of the complex synergies, trade-offs and context dependencies involved for the effects of NNTs that is essential for attaining a sustained provision of ecosystem services.
Invasive Mesquite (Prosopis juliflora), an allergy and health challenge
(MDPI, 2020-01-22) Hussain, M. Iftikhar; Shackleton, Ross T.; El-Keblawy, Ali; Perez, Maria Del Mar Trigo; Gonzalez, Luis
ENGLISH ABSTRACT: Mesquite (Prosopis juliflora (Sw.) DC), is an medium-sized tree (family Fabaceae, subfamily Mimosoideae), that has been intorcuded around the world. It is a noxious invasive species in Africa, Asia, and the Arabian Peninsula and a source of highly allergenic pollen in. The present article reviews the adverse allergenic effects of P. juliflora pollen on human and animal health. Several studies have diagnosed that allergenic pollens from Prosopis spp. can provoke respiratory problems. Prosopis pollen extracts have 16 allergenic components of which nine proteins were recognized as major allergens with some of them showing cross-reactivity. Clinically, understanding Prosopis pollen production, flowering seasonality, pollen load, and dispersal in the atmosphere are important to avoid allergic consequences for local inhabitants. Climate change and other pollution can also help to further facilitate allergenic issues. Furthermore, we document other human and animal health problems caused by invasive Prosopis trees. This includes flesh injuries, dental and gastric problems, and the facilitation of malaria. This review summarizes and enhances the existing knowledge about Prosopis flowering phenology, aeroallergen, and other human and animal health risks associated with this noxious plant.
Motivations and contributions of volunteer groups in the management of invasive alien plants in South Africa’s Western Cape province
(South African National Biodiversity Institute, 2021-07-08) Jubase, Nolwethu; Shackleton, Ross T.; Measey, John
ENGLISH ABSTRACT: Background: Research and management of biological invasions traditionally focuses on state operated large scale control initiatives, with little emphasis on volunteers. Volunteering can, however, contribute to detection, eradication and containment of invasive alien plant species (IAPS). Understanding the extent of involvement of volunteers in invasive alien species management is important. Similarly, understanding volunteers’ motivations to volunteering is important to improve the success of invasive alien species management. Objective: In this study we aimed to: 1) identify volunteer groups controlling IAPS in the Western Cape province of South Africa, 2) understand their practices and contributions towards detecting and controlling IAPS, 3) examine volunteer’s motivations for controlling IAPS, and, 4) identify the challenges individual volunteers and groups face. Methods: The data were collected using online questionnaires. Results: In total, we identified 52 volunteer groups. We broadly estimate that these groups clear nearly 8000 ha of land with estimated labour costs of ZAR 6.5 million annually (equivalent to USD 0.38 million) when aligned with formal state management cost estimates. Most volunteer groups raise their own funds to facilitate their work, however, many suggest support from government entities, landowners and Non-Government Organisations would help. Most volunteers (82%) detect and report invasive species to their team leaders, citizen science platforms and relevant authorities. Volunteers themselves gain physical and psychological fulfilment and build their social capital by meeting new people. Conclusion: Our findings point to the valuable contribution of these groups, but also the need for better co-ordination and engagement between volunteer groups and mandated authorities on science, policy and management
Prosopis : a global assessment of the biogeography, benefits, impacts and management of one of the world’s worst woody invasive plant taxa
(Oxford University Press on behalf of the Annals of Botany Company, 2014) Shackleton, Ross T.; Le Maitre, David C.; Pasiecznik, Nick M.; Richardson, David M.; Dukes, Jeffrey S.
Invasive species cause ecological, economic and social impacts and are key drivers of global change. This is the case for the genus Prosopis (mesquite; Fabaceae) where several taxa are among the world's most damaging invasive species. Many contentious issues (‘conflicts of interest’) surround these taxa, and management interventions have not yet sustainably reduced the negative impacts. There is an urgent need to better understand the factors that drive invasions and shape management actions, and to compare the effectiveness of different management approaches. This paper presents a global review of Prosopis, focusing on its distribution, impacts, benefits and approaches to management. Prosopis was found to occur in a 129 countries globally and many more countries are climatically suitable. All areas with naturalized or invasive Prosopis species at present are suitable for more taxa and many Asian and Mediterranean countries with no records of Prosopis are bioclimatically suitable. Several Prosopis species have substantial impacts on biodiversity, ecosystem services, and local and regional economies in their native and even more so in their invasive ranges; others provide multiple benefits to local communities. Management efforts are underway in only a small part of the invaded range. Countries where more research has been done are more likely to implement formal management than those where little published research is available. Management strategies differ among countries; developed nations use mainly mechanical and chemical control whereas developing nations tend to apply control through utilization approaches. A range of countries are also using biological control. Key gaps in knowledge and promising options for management are highlighted.
Public awareness and perceptions of invasive alien species in small towns
(MDPI, 2021-12-14) Jubase, Nolwethu; Shackleton, Ross T.; Measey, John
Invasive alien species (IAS) are a growing threat globally and cause a variety of ecological, economic, and social impacts. People can introduce IAS and facilitate their spread, and can also implement, support, or oppose their management. Understanding local knowledge, awareness, and perceptions are therefore crucial if management and policy are to be effective. We administered questionnaires to members of the public in eight small towns along the Berg River Catchment in the biodiverse fynbos biome of South Africa. We aimed to assess: (1) awareness of IAS by the general public, (2) local perceptions of the impacts associated with IAS, (3) whether awareness of IAS is correlated with demographic covariates and IAS density, and (4) people’s willingness to detect, report, and support IAS management. Overall, 262 respondents participated in the survey. Most respondents (65%) did not know what IAS are, and 10% were unsure. Many respondents also perceived IAS as beneficial. Using a logistic regression, we found that IAS density, educational level, and gender influenced people’s knowledge and perceptions about IAS in the region. There were a small number (4%) of respondents currently detecting and reporting IAS, but many respondents were interested to learn more. We concluded that people living in small towns in the Western Cape of South Africa remain largely unaware of IAS and their impacts. It is crucial to increase awareness-raising initiatives, and build support and engagement in management of IAS in small towns.
Use of non-timber forest products from invasive alien Prosopis species (mesquite) and native trees in South Africa : implications for management
(Springer, 2015) Shackleton, Ross T.; Le Maitre, David C.; Van Wilgen, Brian W.; Richardson, David M.
Background: Prosopis species have been introduced to many areas outside their native range to provide benefits to local communities. Several Prosopis species and their hybrids (hereafter “mesquite”) have, however, become naturalised and invasive and now generate substantial costs. Management options are limited because of the complex conflicts of interest regarding benefits and costs. Management policies and strategies must take account of such conflicts, but further insights are needed on the dimensions of uses and impacts before such information can be usefully applied. Current policy in South Africa allows for the growth and use of mesquite in one province, but not in others where its control is mandatory. We report on a study to quantify the direct use and perceptions of non-timber forest products (NTFPs) from mesquite and native trees in South Africa. Methods: Semi-structures household interviews were conducted with various stakeholder groups to identify what tree products are used, to ascertain amounts used as well as to gauge perceptions of natural resource use between different tree species and use over time. Results: The direct household use value of native trees was higher than that of mesquite, and local stakeholders attached greater value to products from native trees than from mesquite. Therefore, native trees are and will still be preferentially harvested, and mesquite is unlikely to offer protection to native species by providing an alternative source of products. Mesquite pods do, however, provide valuable additional resources (fodder and medicinal products). The use of both native trees and mesquite is decreasing as the incomes of poorer households rise and as alternative energy sources become available. The benefits and reliance on mesquite are not as high as previously assumed and the impacts from mesquite invasions create large problems for local communities. Conclusion: This study provides further evidence that the impacts of mesquite exceed the benefits, lending support for a policy to reduce negative impacts.

Browsing by Author "Shackleton, Ross T."

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