Ross T. Shackleton’s research while affiliated with Stellenbosch University and other places

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Publications (24)


Fig. 2. The study site located in the natural Sahara -Sindian Forest of southern Iran.
Fig. 3. Soil sampling under and outside the canopy of P. cineraria (a and c) and P. juliflora (b and d). Solid black arrows indicate crown edge, and red dashed arrows indicate Tree crown Diameter (TCD).
Native versus non-native Prosopis woody species: Which fertilize the soil better?
  • Article
  • Full-text available

January 2025

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6 Reads

Folia Oecologica

Maryam Moslehi

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Farzad Ahmadi

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[...]

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Ross T. Shackleton

This study assessed differences in the physical, chemical, and microbial properties of soils under trees of the native species Prosopis cineraria and the invasive species Prosopis juliflora trees, focusing on implications for ecosystem management and restoration. At the start of the growing season, 30 trees of each species with a trunk diameter of 15–30 cm were randomly selected. Soil samples were taken from the top 20 cm of soil profiles east of each tree, under the tree crowns and from control plots in open areas. Three soil samples per site were pooled for chemical and microbial analysis. Soil moisture was highest under P. cineraria (14.64 ± 0.3) and lowest in control plots (9.04 ± 0.65). Soil pH was highest in control soils (7.91 ± 0.09), slightly lower under P. cineraria (7.77 ± 0.06), and lowest under P. juliflora (7.49 ± 0.0). Electrical conductivity, soil salinity was highest under P. juliflora (2.25 ± 0.12). Microbial activity indicators (basal respiration and microbial biomass carbon) were greater under P. cineraria than under P. juliflora trees. Native P. cineraria trees enhance soil conditions, benefiting ecosystem management. In contrast, invasive P. juliflora trees raise soil salinity, threatening soil quality, biodiversity, and ecosystem services in the Sahara-Sahel region. Managing the spread of P. juliflora is crucial to maintaining ecosystem functions.

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Framing challenges and polarized issues in invasion science: toward an interdisciplinary agenda

October 2024

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454 Reads

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1 Citation

BioScience

In a hyperconnected world, framing and managing biological invasions poses complex and contentious challenges, affecting socioeconomic and environmental sectors. This complexity distinguishes the field and fuels polarized debates. In the present article, we synthesize four contentious issues in invasion science that are rarely addressed together: vocabulary usage, the potential benefits of nonnative species, perceptions shifting because of global change, and rewilding practices and biological invasions. Researchers have predominantly focused on single issues; few have addressed multiple components of the debate within or across disciplinary boundaries. Ignoring the interconnected nature of these issues risks overlooking crucial cross-links. We advocate for interdisciplinary approaches that better integrate social and natural sciences. Although they are challenging, interdisciplinary collaborations offer hope to overcome polarization issues in invasion science. These may bridge disagreements, facilitate knowledge exchange, and reshape invasion science narratives. Finally, we present a contemporary agenda to advance future research, management, and constructive dialogue.


Gauging the threat of invasive species to UNESCO world heritage sites relative to other anthropogenic threats

September 2024

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94 Reads

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1 Citation

Biological Invasions

There are 230 UNESCO World Heritage Sites that were designated based on their important natural features. These represent some of the most iconic and important natural places on Earth, with immense value for biodiversity conservation, ecosystem service supply and cultural well-being. Many of these sites are degraded by anthropogenic drivers, including socioeconomic factors (population growth, poverty and tourism), extractive activities (logging, mining, and hunting), external threats (fire, climate change, land-use change, pollution), and biological threats (disease and invasive species). Of these, invasive species remain one of the most problematic for management, and once introduced, populations can grow exponentially and spread to other locations even when actively managed. Given the economic and environmental threats imposed by invasive species, we asked how they compare to the other anthropogenic threats. We reviewed the primary literature for each World Heritage Site and scored the prevalence of 12 different anthropogenic drivers. We found that invasive species rank as one of the most frequently identified threats and pose the greatest degree of concern compared to all other threats, on par with the threat from pollution and greater than logging, land-use change and climate change. We compared our scoring, based on review of the literature, with that of the UNESCO and IUCN monitoring reports. Although there was general agreement between these two assessments, the literature provided information on 55 sites not included in the monitoring reports. We further examine the invasive species examined in the articles and the degree of their perceived impacts on biodiversity, habitat, rare species, ecosystem function, tourism, and economic impacts. It is important that invasive species are well monitored and managed in WHSs to reduce their impacts and meet policy mandated targets and conservation goals.


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Abandoned croplands show higher insectivorous bat species and functional diversity than forest fragments in a communal land area of the Eastern Cape, South Africa

July 2024

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96 Reads

Deagrarianisation (cropland, field abandonment) is a widespread global phenomenon with high potential for carbon sequestration and for reversing biodiversity extinction debt thus promoting environmental sustainability and conservation. To date, much work on this topic has focused on plant succession and associated plant diversity, but few studies have considered faunal communities, particularly in Africa. Here we used passive acoustic monitoring to record insectivorous bat communities within forest fragments and former fields under communal land tenure in the Transkei region (Eastern Cape) of South Africa. Insectivorous bat diversity of fields, abandoned in the 1960s to 1980s, resembling late stages of succession, were compared to fragments of Transkei Coastal Scarp forest embedded within the landscape. We found that former fields hosted 14 species from 11 genera, comprising greater species richness, activity, Shannon-Weiner diversity, and functional diversity, irrespective of age, as compared to the forest fragments. Furthermore, the former fields exhibited comparable species richness to, and higher functional diversity than, three large neighbouring intact Transkei Scarp forests. Interestingly, the time since cultivation had ceased (35—64 years ago) had no measurable effect on species and functional diversity. Former fields are dominated by the invasive alien shrub Lantana camara and the indigenous pioneer tree Vachellia karoo , but nonetheless in terms of insectivorous bats, these landscapes have a conservation value as they are diverse both in terms of species and function. Mutual mechanisms to enhance both biodiversity conservation and the utility of the land to local communities should be further considered.



Main goals and recommendations of the Global Guidelines for the use of Non‐Native Trees (GG‐NNTs; reproduced with permission from Brundu et al., 2020). INNTs, Invasive Non‐Native Trees.
Stakeholders' perceptions of non‐native trees (NNTs) according to the sector they work in. Percentages indicate the percentage of stakeholders from each sector that scored the first three words that immediately came to their mind when they thought about NNTs as negative (left), neutral (centre) and positive (right).
Level of agreement and polarization of survey respondents on 14 Likert (ranking) statements. Statements with low polarization (i.e. greater consensus among respondents) are indicated in black, medium polarization in orange, and high polarization (i.e. high disagreement among respondents) in red.
Relationship between sociodemographic characteristics of respondents and their response patterns in each of the five factors related to the benefits and negative impacts of non‐native trees (NNTs) and to whether the use of NNTs should be avoided, it is acceptable to use NNTs that pose low invasion risk, or it is acceptable to use all NNTs. Shapes and horizontal lines indicate the differences from baseline logits [vertical grey line] at 95% CI values. Positive and negative estimates indicate, respectively, whether respondents agree or disagree to a greater extent than the comparison/baseline group. Filled shapes indicate significant differences from the baseline group (*p < 0.05; **p < 0.01; ***p < 0.001). The categorical group with the greatest number of respondents is the baseline group for each of the sociodemographic variables. Numbers in parentheses indicate the number of respondents in each group. Only groups with more than five respondents were used.
Stakeholders' compliance with the GG‐NNTs according to the sector they work in. DYO = ‘Does your organization’. [Correction added on 17 June, after first online publication: The formatting of Figure 5 has been corrected.]
Stakeholders' views on the global guidelines for the sustainable use of non‐native trees

June 2024

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536 Reads

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3 Citations

A large number of non‐native trees (NNTs) have been introduced globally and widely planted, contributing significantly to the world's economy. Although some of these species present a limited risk of spreading beyond their planting sites, a growing number of NNTs are spreading and becoming invasive leading to diverse negative impacts on biodiversity, ecosystem functions and human well‐being. To help minimize the negative impacts and maximize the economic benefits of NNTs, Brundu et al. developed eight guidelines for the sustainable use of NNTs globally—the Global Guidelines for the Use of NNTs (GG‐NNTs). Here, we used an online survey to assess perceptions of key stakeholders towards NNTs, and explore their knowledge of and compliance with the GG‐NNTs. Our results show that stakeholders are generally aware that NNTs can provide benefits and cause negative impacts, often simultaneously and they consider that their organization complies with existing regulations and voluntary agreements concerning NNTs. However, they are not aware of or do not apply most of the eight recommendations included in the GG‐NNTs. We conclude that effectively managing invasions linked to NNTs requires both more communication efforts using an array of channels for improving stakeholder awareness and implementation of simple measures to reduce NNT impacts (e.g. via GG‐NNTs), and a deeper understanding of the barriers and reluctance of stakeholders to manage NNT invasions. Read the free Plain Language Summary for this article on the Journal blog.


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Gauging the threat of invasive species to UNESCO World Heritage Sites relative to other anthropogenic threats.

June 2024

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153 Reads

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1 Citation

There are 230 UNESCO World Heritage Sites that were designated based on their important natural features. These represent some of the most iconic and important natural places on Earth, with immense value for biodiversity conservation, ecosystem service supply and cultural well-being. Many of these sites are degraded by anthropogenic drivers, including socioeconomic factors (population growth, poverty and tourism), extractive activities (logging, mining, and hunting), external threats (fire, climate change, land-use change, pollution), and biological threats (disease and invasive species). Of these, invasive species remain one of the most problematic for management, and once introduced, populations can grow exponentially and spread to other locations even when actively managed. Given the economic and environmental threats imposed by invasive species, we asked how they compare to the other anthropogenic threats. We reviewed the primary literature for each World Heritage Site and scored the prevalence of 12 different anthropogenic drivers. We found that invasive species rank as one of the most frequently identified threats and pose the greatest degree of concern compared to all other threats, on par with the threat from pollution and greater than logging, land-use change and climate change. We compared our scoring, based on review of the literature, with that of the UNESCO and IUCN monitoring reports. Although there was general agreement between these two assessments, the literature provided information on 55 sites not included in the monitoring reports. We further examine the invasive species examined in the articles and the degree of their perceived impacts on biodiversity, habitat, rare species, ecosystem function, tourism, and economic impacts. It is important that invasive species are well monitored and managed in WHSs to reduce their impacts and meet policy mandated targets and conservation goals.


The impact of the invasive alien plant Vernonanthurapolyanthes on conservation and livelihoods in the Chimanimani uplands of Zimbabwe

March 2024

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185 Reads

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1 Citation

Biological Invasions

Biological invasions can have major social-ecological consequences for rural communities across the world. However, the dimensions (characteristics, infestation and socio-ecological impacts) of emerging invasive alien plants are often less known and urgent information is needed to guide policy and management. In light of this, this paper assesses the social-ecological impacts of Vernonanthura polyanthes, an emerging invasive alien plant found in a Zimbabwean upland landscape which supports conservation and livelihoods. The paper employs qualitative methods—community mapping, time series analysis, and key informant interviews—involving individuals from diverse socio-economic backgrounds, to examine the socio-ecological and economic implications of V. polyanthes and its management in Chimanimani, Zimbabwe. We found that there are nuanced perspectives regarding this invasive alien plant among different socio-economic groups in the region who have different experiences of living with V. polyanthes. Some are embracing it for apiculture, firewood, and ethnomedicine while, on the other hand, some see the tree as negatively affecting key livelihoods (crop farming, pastoralism, and tourism) that are common in the region. Local people also identified that V. polyanthes is associated with ecological impacts that include loss of biodiversity, promoting pests, and negatively affecting watersheds and associated water sources. These mixed experiences concerning the plant are leading to different management practices, in turn inducing some conflicts among various actors. Based on our findings, we suggest more should be done to better manage this invasive alien plant in the region before negative impacts become too great, particularly in protected areas.


Advancing forest inventorying and monitoring

February 2024

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614 Reads

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6 Citations

Annals of Forest Science

Forests are under pressure and going through rapid changes. However, current inventorying and monitoring (IM) programs are often either disjointed, too narrow in their scope and/or do not operate at fine enough temporal resolutions, which may hinder scientific understanding, the timely supply of information, fast decision making, and may result in the sub-optimal use of resources. For these reasons, there is an urgent need for Advanced Forest Inventorying and Monitoring (AIM) programs to (i) achieve expanded relevance (by augmenting data/information across ecosystem properties and trophic levels), (ii) have increased temporal resolution (by tailored data collection frequency), and (iii) make use of technological advances (by incorporating novel tools and technologies). The Advanced Inventorying and Monitoring for Swiss Forests (SwissAIM) initiative was launched in 2020 to address these needs. SwissAIM builds upon the foundation offered by the existing programs (e.g., national forest inventory, long-term forest ecosystem research, biodiversity monitoring). It aims to offer a collaborative and adaptive framework to enable integrated data collection, evaluation, interpretation, analysis, and modeling. Ideally, it will result in a more responsive system with respect to current and predicted biotic/abiotic stressors that will challenge Swiss forests. Developing such a system implies identifying the information needs of different stakeholders (e.g., science, policy, practice), related technical requirements, and governance frameworks. Here, we present (i) the main features of the SwissAIM initiative (vision, scientific questions and variables, governance and engagement), (ii) the main outcomes of the participatory design process (measurements, sampling, and plot design), (iii) the potential transferability of AIM initiatives outside Switzerland (timing, relevance, practicability), and (iv) the key messages that emerged (i.e., need for advancement, integration and transdisciplinarity, statistical underpinning). Since similar needs related to forest inventorying and monitoring are emerging throughout Europe and elsewhere, the objective of this opinion paper is to share our experience and promote a dialog with those interested in developing AIM initiatives in other countries and regions.


Citations (17)


... Rewilding focuses on restoring entire ecosystems by enhancing ecological processes rather than targeting specific species or habitats. Effective rewilding strengthens ecosystem resilience to invasions and stressors; however, the unpredictability of species recolonization raises legitimate concerns (Guareschi et al. 2024 ). The challenges facing invasion science are not solely technical or logistical in nature. ...

Reference:

Conceptual and Ethical Considerations in Invasion Science
Framing challenges and polarized issues in invasion science: toward an interdisciplinary agenda

BioScience

... These effects might have been detected due to both the ease of access to these places for research and their increased human visitation due to tourism and recreation (Anderson et al. 2015;Shackleton et al. 2020). For World Heritage Sites in particular, biological invasions have been ranked as among the highest threats, commensurate to other drivers such as pollution, logging, land use and climate change (Cadotte et al. 2024 in review). Considering that these types of protected areas are typically reserved for stricter protection, the detection of non-native species' effects in these locations is concerning, given that these places are especially crucial for biodiversity conservation and addressing climate change and are potentially the most likely to expand under the Global Biodiversity Framework. ...

Gauging the threat of invasive species to UNESCO world heritage sites relative to other anthropogenic threats

Biological Invasions

... Sax and colleagues (2022 ) stressed how beneficial outcomes of some nonnative species may be common and important for human well-being (e.g., relational, instrumental, and intrinsic values). However, different stakeholders may have contrasting perspectives (i.e., environmental, economic, social, ethic, or aesthetic), different assessment systems, and different priorities, making it difficult to achieve feasible trade-offs (Woodford et al. 2016, Oficialdegui et al. 2020, Novoa et al. 2024 ). These perspectives are value laden and may not align with a simplistic for or against narrative. ...

Stakeholders' views on the global guidelines for the sustainable use of non‐native trees

... The global vegetation composition has been adversely impacted by a variety of anthropogenic activities, including livestock grazing, tourism, agricultural expansion, and so forth. These activities have also led to the introduction or spread of invasive species [44][45][46]. ...

The impact of the invasive alien plant Vernonanthurapolyanthes on conservation and livelihoods in the Chimanimani uplands of Zimbabwe

Biological Invasions

... Monitoring trees is essential for addressing biodiversity loss and climate change, maintaining ecosystem services, and guiding global conservation and restoration efforts [6,18]. Tree data serve to provide baselines, track changes over time, train and validate ecological models, as well as inform policies and decision making [9]. While forest inventories provide high-quality tree data, such as species and ground measurements, they are labor-intensive, costly, and often limited in spatial and temporal scope [9]. ...

Advancing forest inventorying and monitoring

Annals of Forest Science

... Similar to findings in other temperate countries, research on the effects of increment coring on various tree species has shown no significant differences in decay and mortality between cored and uncored Norway spruce (Picea abies (L.) H.Karst.) and European beech (Fagus sylvatica L.) trees [16][17][18]. Similarly, no significant differences in mortality rates were found between cored and uncored samples of white fir (Abies concolor (Gordon & Glend.) ...

No evidence that coring affects tree growth or mortality in three common European temperate forest tree species

European Journal of Forest Research

... soil and biodiversity protection) (cf. Haas et al., 2019, Pham et al., 2023, Bayrak et al., 2013, Nguyen and Kull 2022Nambiar et al., 2015Nambiar et al., , 2018. ...

Factors influencing farmers' forestland-use changes over 15 years (2005–2020) in Thua Thien Hue province, Vietnam

International Forestry Review

... Alpha is a parameter used to measure the weight given to recent values in comparison with historic ones, and Beta is a parameter used to measure the weight given to the recent trend in comparison with the historical trend www.kva.se/en Observed deforestation reduction in Vietnam has been linked to conservation policies (TranQuoc et al. 2023) and poverty reduction interventions(Van Khuc et al. 2018). ...

Factors associated with deforestation probability in Central Vietnam: a case study in Nam Dong and A Luoi districts

Journal of Forest Research

... The focus is on understanding the network of relationships and interactions through which power is exercised, recognizing that power is shaped by complex social networks rather than solely formal positions or policies. Analyzing these network dynamics reveals how power is distributed, negotiated, and contested within the tourism and conservation landscape (Arts et al., 2018;Shackleton et al., 2023). Evaluating power dynamics is key to the role of animals (Edelblutte et al., 2023). ...

Navigating power in conservation

... Another example of an ornamental woody plant that is outcompeting local plants with detrimental effects on local ecosystems is the Chinese windmill palm (Trachycarpus fortune). This Southeast-Asian palm has naturalized ranges in Europe, North America, and South America (Genazzi et al., 2022). South of the European Alps, it changes the understory composition of forests, outcompeting native woody saplings, and resulting in higher fire and gravitational hazards such as landslides or avalanches (Genazzi et al., 2022;Tonellotto et al., 2022). ...

People's knowledge and perceptions of Trachycarpus fortunei (Chinese windmill palm) invasions and their management in Ticino, Switzerland

Geographica Helvetica