The detrimental impacts of invasive alien species (IAS) on ecosystem goods and services and local and regional economies are well documented. However, the use of IAS by rural communities is little understood, and rarely factored into IAS control programmes. Understanding the use of IAS by rural communities and factoring these into cost-benefit models is complex, depending upon a range of local-level attributes such as the time since invasion, abundance, and local-level costs and benefits. This paper reports on two case studies examining the role of IAS in rural livelihoods in the Eastern Cape, South Africa. In both cases, rural communities made widespread consumptive use of the IAS and generally would prefer higher densities, except in certain key localities. Several households traded in IAS products to generate supplementary income. We present a conceptual framework to guide interpretation of these and future case studies, considering attributes such as time since invasion, the competitiveness of the species, and the relative costs and benefits.

Deagraianisation is a worldwide phenomenon with widespread social, ecological and economic effects yet with little consensus on the local or higher level causes. There have been contested views on the causes and consequences of deagrarianisation on South Africa’s Wild Coast, which is an international biodiversity hotspot. Using GIS, household interviews and ecological sampling, we compared the perspectives of current and former cultivators as to why some have abandoned farming, whilst also tracking the uses and woody plant cover and composition of fields abandoned at different periods. The GIS analysis showed that field abandonment had been ongoing over several decades, with a decline from 12.5 % field cover in 1961 to 2.7 % in 2009. The area of forests and woodlands almost doubled in the corresponding period. There was a distinct peak in field abandonment during the time of political transition at the national level in the early 1990s. This political change led to a decrease in government support for livestock farming, which in turn resulted in reduced animal draught power at the household and community level, and hence reduced cropping. The study showed it is largely the wealthier households that have remained in arable agriculture and that the poorer households have abandoned farming. The abandoned fields show a distinct trend of increasing woody biomass and species richness with length of time since abandonment, with approximately three woody plant species added per decade. Most local respondents dislike the increases in forest and woodland extent and density because of anxiety about wild animals causing harm to crops and even humans, and the loss of an agricultural identity to livelihoods and the landscape.

The negative impacts of invasive alien species on the environment are well documented. However, despite the predominantly negative perceptions associated with invasive species, it is evident that a number of these plants have been part of the landscape for generations and have numerous commercial and non-market uses. Consequently, there is a need for research that considers the impact of invasive species on the livelihoods and well-being of local communities. The authors investigated the contribution that the trade in prickly pear (Opuntia ficus-indica), an invasive alien species, makes to the household income streams of poor trading households. The research highlights the apparent conflict of interests and trade-offs that exists between local traders, for whom the sale of the prickly pear provides a livelihood source, and the South African Government, who are actively seeking to remove the plant from the landscape.

The frequency of fire has increased in savannas yet few studies have assessed how plants persist when subjected to long‐term disturbance by fire. We investigated the contributions of bark thickness and resprouting to the persistence of woody plants in two fire trials that were started in 1948 and 1949. The number of resprouts per individual, bark thickness, basal diameter and height of woody plants were measured in unburnt plots and those burnt annually, triennially and quinquennially during the late dry season. Changes in tree density, number of resprouts and individuals in different height classes between 1963 and 2002 were assessed. Bark thickness varied among species and also increased with increases in basal diameter. Generally, plants with thick bark survived fire more than those with thin bark. Resprouting was the major fire survival strategy for most species. The number of resprouts produced per plant ranged from 4 ± 3 (Acacia rehmanniana) to 14 ± 9 (Pseudolachnostylis maprouneifolia). Fire reduced species richness in plots burnt annually and triennially by 47% and 6% respectively. Species richness increased in unburnt plots (5%) and those burnt quinquennially (16%). Most woody species survived fire through a combination of traits.

Aim We examined differences in the architecture of African and Australian savanna trees. We sought to attribute variation in tree architecture to current environments, wood density and phylogeny, and thereby elucidate the relative importance of biogeographic idiosyncrasies versus current factors in underpinning architectural differences. Location Africa and Australia. Methods We compiled canopy diameters and stem diameters from 4867 trees of 97 species and heights and stem diameters from 10,786 trees of 155 species from a range of African and Australian savanna ecosystems and climates. Using Bayesian methods we first estimated continental‐scale savanna tree allometries, ignoring species differences. We then examined continental differences in species‐specific allometries accounting for trait covariation using a phylogeny of our study species. Environmental variables and wood density data were included as covariates, allowing us to assess the potential underpinning of regional differences in tree allometries by differences in current environments and traits. Results Substantial allometric differences exist between Australian and African savanna trees. Australian trees are on average 6 m taller at 20 cm diameter, with a 53% smaller canopy area than African trees. However, this extreme continental‐scale variation is driven by the architecture of only a few taxa in this study – Vachellia and Senegalia versus Eucalyptus and Corymbia – rather than systematic differences between species, wood density and environment. These same genera often dominate the woody strata of South African and Australian savannas, respectively. Main conclusions Stark differences in the architecture of African and Australian savanna tree taxa are not a product of environmental differences and are not consistent across species. Rather, the most likely explanation is the different evolutionary histories of African and Australian savannas, which share no woody species. We consider that these architectural differences are likely to impact regional patterns of woody biomass accumulation.

Woody plant invasions, either of alien or indigenous species, are deemed to result in loss of ecosystem goods and services in many areas throughout the world, resulting in significant degradation and economic costs. Invasion of Euryops floribundus, a species indigenous to South Africa, is perceived to have reduced the grazing available for domestic livestock. Consequently, a programme of manual eradication has been implemented to improve the grazing resource and provide jobs for poverty alleviation. However, there is potential for a conflict of interest as our study shows that almost all households rely on Euryops for fuel and at times fencing material, whereas only a minority of households own livestock. Moreover, comparison of invaded and non-invaded sites indicated that the invaded sites harbour greater plant species richness and higher grass culm density per unit area of grass cover, as well as higher forb and litter cover. While invaded sites had lower grass cover, overall plant cover was no different between invaded and non-invaded sites. Multivariate analysis indicated no obvious differentiation in community composition between invaded and non-invaded areas, suggesting stronger drivers of community composition other than Euryops invasion presumed to be facilitated by the effects of high livestock densities. Overall, our study suggests that the clearing operation may well benefit from a better understanding of the social needs, perceptions of degradation by the various stakeholders and ecological dynamics of the area, especially local reliance on the resources, and the dynamics of the invasion, particularly its extent, rate of spread and susceptibility for re-invasion in the cleared areas.

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