The effect of spatial scale on the use of biodiversity surrogates and socio-economic criteria in systematic conservation assessments

[摘要] A systematic conservation assessment is the first phase of a systematic conservation planningprotocol; it uses spatial data and representation targets for the setting of priority areas and theassessment of risk to biodiversity. This thesis describes the findings of investigations on the use ofdata in systematic conservation assessments.Conservation planning can be done at different spatial scales (from global to local). SystematicConservation planning can be done at different spatial scales (from global to local). Systematicconservation assessments rely on the use of surrogates for biodiversity and often, as well, socioeconomiccriteria. Biodiversity surrogates can be classified as taxonomic, community andenvironmental. In Chapter 2, a literature review was performed (i) to quantify the use of biodiversitysurrogates and socio-economic criteria in conservation assessments; and (ii) to test the hypothesis thatsurrogates are chosen in respect to the hierarchical organisation of biodiversity. In other words, finescale conservation assessments are correlated with taxonomic surrogates, large scale conservationassessments are correlated with environmental surrogates, and assemblage surrogates are assessed atan intermediary scale. The literature review was based on a structured survey of 100 ISI journalpublications. The analysis revealed that spatial scale had a weak effect on the use of biodiversitysurrogates in conservation assessments. Taxonomic surrogates were the most used biodiversitysurrogates at all scales. Socioeconomic criteria were used in many conservation assessments. I arguethat it is crucial that assemblage and environmental data be more used at larger spatial scales.The allocation of conservation resources needs to be optimised because resources are scarce. Aconservation assessment can be a lengthy and expensive process, especially when conducted at finescale.Therefore the need to undertake a fine-scale conservation assessment, as opposed to a morerapid and less expensive broader one, should be carefully considered. The study of Chapter 3 assessedthe complementarity between regional- and local-scale assessments and the implications on the choiceof biodiversity features at both scales. The study was undertaken in Réunion Island. A biodiversityassessment was performed at a regional scale and measured against a finer-scale assessmentperformed over a smaller planning domain. Two datasets composed of species distributions, habitatpatterns and spatial components of ecological and evolutionary processes were compiled asbiodiversity surrogates at each scale. Targets for local-scale processes were never met in regionalassessments, while threatened species and fragmented habitats were also usually missed. The regionalassessment targeting habitats represented a high proportion of local-scale species and habitats at targetlevel (67%). On the contrary, the one targeting species was the least effective. The results highlightedthat all three types of surrogates are necessary. They further suggested (i) that a spatial strategy basedon a complementary set of coarse filters for regional-scale assessments and fine filters for local-scaleones can be an effective approach to systematic conservation assessments; and (ii) that information onhabitat transformation should help identify where efforts should be focused for the fine-scale mappingof fine filters. Together with priority-area setting, the identification of threatened biodiversity features hashelped to prioritise conservation resources. In recent years, this type of assessment has been appliedmore widely at ecosystem-level. Ecosystems can be categorised into critically endangered, endangeredand vulnerable, following the terminology of the IUCN Red List of threatened species. Various criteriasuch as extent and rate of habitat loss, species diversity and habitat fragmentation can be used toidentify threatened ecosystems. An approach based only on the criterion of the quantification ofhabitat loss was investigated in Chapter 4 for the Little Karoo, South Africa. Habitat loss withinecosystem type is quantified on land cover information. The study analysed the sensitivity of thecategorisation process to ecosystem and land cover mapping, using different datasets of each. Threeecosystem classifications and three land cover maps, of different spatial resolutions, were used toproduce nine assessments. The results of these assessments were inconsistent. The quantification ofhabitat loss varied across land cover databases due to differences in their mapping accuracy. It wasreflected on the identification of threatened ecosystems of all three ecosystem classifications. Lessthan 14% of extant areas were classified threatened with the coarsest land cover maps, in comparisonto 30% with the finest one; and less than 9% of ecosystem types were threatened with the coarsest landcover maps, but between 15 and 23% were threatened with the finest one. Furthermore, the resultssuggested that the identification of threatened ecosystems is more sensitive to the accuracy of habitatloss quantification than the resolution of the ecosystem classification. Detailed land cover mappingshould be prioritised over detailed ecosystem maps for this exercise.This thesis highlighted the importance of ecosystems and processes as biodiversity surrogates inconservation assessments and suggested that results of conservation assessments based on these data,should be more widely presented in published articles. Finally, it also made apparent the importantrole of mapping habitat transformation for systematic conservation plans.

[发布机构] Stellenbosch University