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The ability to predict which areas of conservation importance are most vulnerable to transformation and to rank the relative damage that transforming land uses could cause to biodiversity are important components of an effective and realistic conservation planning process. We used the South African grassland biome as a case study to illustrate the assessment of vulnerability to land-use transformation through the construction of a “threat map.” We identified the dominant transforming land uses and created suitability models based on area appropriateness for each. Land uses were scored according to their expected relative impacts on biodiversity, with a framework that included compositional, structural, and functional components. This information, once combined, resulted in a map that highlighted the areas most vulnerable to transformation in terms of the likelihood of their transformation and the impact on their biodiversity. We propose that such an analysis of the threat of transformation, in combination with species-representation approaches, will aid the integration of conservation planning theory and decision making. This approach can be applied at any scale and in any region with a robustness and accuracy dependent on data quality, resultant suitability models, and comprehension of how land uses affect an area's biodiversity. [ABSTRACT FROM AUTHOR]

To assess the correspondence between current avian distributions in the lowlands of northern South America with respect to the hypothesized importance of sea level rise and other events over the past 15 million years on speciation. Tropical lowlands of north-western South America. To establish which bird taxa may have originated in each area of endemism, I examined the ranges of all bird species occurring in the Pacific and the Caribbean lowlands. To determine land and sea distribution during a sea level rise of 100 m in north-western South America and eastern Central America, I traced the 100 m contour line from the Geoatlas of Georama and the Global 30-Arc-Second Elevation Data (GTOPO30) produced by the US Geological Survey. During a sea level rise of ∼100 m, marine incursions would have occurred from the Caribbean Sea and the Pacific Ocean. Several areas of tropical forest and dry/arid vegetation would have been isolated, currently known as the Darién, Chocó, Nechí, Catatumbo, Tumbesian and Guajiran areas of animal and plant endemism. A large part of the high diversity of forest and nonforest birds and other animals and plants in the Pacific rain forest and the Caribbean woodland likely arose as the result of sea level rises, dispersal and other geological and climatic events. [ABSTRACT FROM AUTHOR]

Aim Models of the potential distributions of invading species have to deal with a number of issues. The key one is the high likelihood that the absence of an invading species in an area is a false absence because it may not have invaded that area yet, or that it may not have been detected. This paper develops an approach for screening pseudo-absences in a way that is logical and defensible. Innovation The step-wise approach involves: (1) screening environmental variables to identify those most likely to indicate conditions where the species cannot invade; (2) identifying and selecting the most likely limiting variables; (3) using these to define the limits of its invasion potential; and (4) selecting points outside these limits as true absence records for input into species distribution models. This approach was adopted and used for the study of three prominent Hakea species in South Africa. Models with and without the false absence records were compared. Two rainfall variables and the mean minimum temperature of the coldest month were the strongest predictors of potential distributions. Models which excluded false absences predicted that more of the potential distribution would have a high invasion potential than those which included them. Main conclusions The approach of applying a priori knowledge can be useful in refining the potential distribution of a species by excluding pseudo-absence records which are likely to be due to the species not having invaded an area yet or being undetected. The differences between the potential distributions predicted by the different models convey more information than making a single prediction, albeit a consensus model. The robustness of this approach depends strongly on an adequate knowledge of the ecology, invasion history and current distribution of that species. [ABSTRACT FROM AUTHOR]

Prevention is the best way to slow the escalation of problems associated with biological invasions. Screening of potential introductions is widely applied for assessing the risk of species becoming invasive. Despite advances in the understanding of the determinants of invasiveness, screening still relies heavily on assessments of the potential of species to ‘fit in’ to the broad environmental conditions of a target region. Most screening systems ask whether species are native to, or are known to be naturalized or invasive in, regions with ‘similar’ climatic/environmental conditions to the target region. The level of similarity required to make the species a high-risk introduction is generally not specified. This paper describes a protocol for making such assessments more objective, using South Africa as a test case. Using nonparametric niche-based modelling (generalized additive model; GAM) calibrated on the current distribution of each South African biome, we mapped regions of the world that are climatically similar to South African biomes. Lists were produced of countries with the largest areas climatically similar to South Africa overall, and to each biome separately. Validation of the usefulness of the approach was sought by evaluating whether the main invasive plant species in South African biomes occur naturally, or have adventive ranges, in regions mapped as analogous to South African biomes. A very large part of the world is climatically similar to South Africa, with eight countries having larger areas of land classified as climatically similar to South African biomes than the total area of South Africa. Almost all the most prominent invasive species in South African biomes occur naturally or are invasive outside their natural range in areas with similar climates to those that occur in parts of South Africa. This confirms the value of objective climate matching in screening protocols. We examined climatic conditions for a representative sample of major invasive plants from other parts of the world. The analysis identified several species that are already invasive in regions that have matched climates in South Africa but that are not yet introduced or, if already present, have not yet invaded large areas. For example, the following known invasive species should be considered high-risk species in South African grasslands: Alliaria petiolata, Cytisus scoparius, Gleditsia triacanthos, Heracleum mantegazzianum, Hieracium pilosella, Juniperus communis, Pinus contorta, P. monticola, P. ponderosa, P. sylvestris, Prunus laurcerasus, and P. serotina. Objectively matched climatic regions are also useful as a first-cut assessment when evaluating species with no invasive history. [ABSTRACT FROM AUTHOR]

A procedure is required for ecosystem studies which is ordered but flexible and directs workers quickly and inexpensively towards answers to key ecological and management questions. The procedure presented in this paper develops an increasingly complex description of the ecosystem. The initial phase consists of a structural and dynamic description of the ecosystem, followed by a description of its utilization. From this phase, key questions are elaborated and, where appropriate, mathematics models are then constructed. The South African Savanna Ecosystem Project (SASEP) provides an example of the manner in which the procedure can be applied. Examples of key ecological questions are cited, and appropriate models for some of these are described. The use of the approach, in the SASEP, is described by reference to its current objectives, defined in terms of twelve key questions. [ABSTRACT FROM AUTHOR]

Abstract A lack of quantitative data on the impact of large herbivores on woody vegetation around watering points in the Kruger National Park gave rise to an in depth study. This paper reports on trends found at two artificial watering points on the basaltic soils in the Satara Land System. As a result of the almost complete lack of woody individuals in the immediate vicinity of the watering points, this area could be described as a ‘sacrifice area’. Shrub density increased with distance from the watering point, with the impact of large herbivores on shrub density extending up to 2.8 km. The practice of providing artificial water in troughs at windmills in the Kruger National Park causes the formation of a multiple ‘piosphere’ effect, with the existence of a zone of high utilization in woody vegetation extending far beyond the sacrifice area. [ABSTRACT FROM AUTHOR]