Modelling the conversion of Colombian lowland ecosystems since 1940: Drivers, patterns and rates

In biologically mega-diverse countries that are undergoing rapid human landscape transformation, it is important to understand and model the patterns of land cover change. This problem is particularly acute in Colombia, where lowland forests are being rapidly cleared for cropping and ranching. We apply a conceptual model with a nested set of a priori predictions to analyse the spatial and temporal patterns of land cover change for six 50-100 km(2) case study areas in lowland ecosystems of Colombia. Our analysis included soil fertility, a cost-distance function, and neighbourhood of forest and secondary vegetation cover as independent variables. Deforestation and forest regrowth are tested using logistic regression analysis and an information criterion approach to rank the models and predictor variables. The results show that: (a) overall the process of deforestation is better predicted by the full model containing all variables, while for regrowth the model containing only the auto-correlated neighbourhood terms is a better predictor; (b) overall consistent patterns emerge, although there are variations across regions and time; and (c) during the transformation process, both the order of importance and significance of the drivers change. Forest cover follows a consistent logistic decline pattern across regions, with introduced pastures being the major replacement land cover type. Forest stabilizes at 2-10% of the original cover, with an average patch size of 15.4 (+/- 9.2) ha. We discuss the implications of the observed patterns and rates of land cover change for conservation planning in countries with high rates of deforestation. (c) 2005 Elsevier Ltd. All rights reserved.

Assessing the Conservation Status and Threats to Priority Plants: a threat assessment approach and case study in South-East Queensland, Australia

bstract: During the Regional Forest Agreement (RFA) process in south-east Queensland, the conservation status of, and threats to, priority vascular plant taxa in the region was assessed. Characteristics of biology, demography and distribution were used to assess the species' intrinsic risk of extinction. In contrast, the threats to the taxa (their extrinsic risk of extinction) were assessed using a decision-support protocol for setting conservation targets for taxa lacking population viability analyses and habitat modelling data. Disturbance processes known or suspected to be adversely affecting the taxa were evaluated for their intensity, extent and time-scale. Expert opinion was used to provide much of the data and to assess the recommended protection areas. Five categories of intrinsic risk of extinction were recognised for the 105 priority taxa: critically endangered (43 taxa); endangered (29); vulnerable (21); rare (10); and presumed extinct (2). Only 6 of the 103 extant taxa were found to be adequately reserved and the majority were considered inadequately protected to survive the current regimes of threatening processes affecting them. Data were insufficient to calculate a protection target for one extant taxon. Over half of the taxa require all populations to be conserved as well as active management to alleviate threatening processes. The most common threats to particular taxa were competition from weeds or native species, inappropriate fire regimes, agricultural clearing, forestry, grazing by native or feral species, drought, urban development, illegal collection of plants, and altered hydrology. Apart from drought and competition from native species, these disturbances are largely influenced or initiated by human actions. Therefore, as well as increased protection of most of the taxa, active management interventions are necessary to reduce the effects of threatening processes and to enable the persistence of the taxa.