The effect of spatial scale on the use of biodiversity surrogates and socio-economic criteria in systematic conservation assessments
Date
2007-12
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
A systematic conservation assessment is the first phase of a systematic conservation planning
protocol; it uses spatial data and representation targets for the setting of priority areas and the
assessment of risk to biodiversity. This thesis describes the findings of investigations on the use of
data in systematic conservation assessments.
Conservation planning can be done at different spatial scales (from global to local). Systematic
Conservation planning can be done at different spatial scales (from global to local). Systematic
conservation assessments rely on the use of surrogates for biodiversity and often, as well, socioeconomic
criteria. Biodiversity surrogates can be classified as taxonomic, community and
environmental. In Chapter 2, a literature review was performed (i) to quantify the use of biodiversity
surrogates and socio-economic criteria in conservation assessments; and (ii) to test the hypothesis that
surrogates are chosen in respect to the hierarchical organisation of biodiversity. In other words, fine
scale conservation assessments are correlated with taxonomic surrogates, large scale conservation
assessments are correlated with environmental surrogates, and assemblage surrogates are assessed at
an intermediary scale. The literature review was based on a structured survey of 100 ISI journal
publications. The analysis revealed that spatial scale had a weak effect on the use of biodiversity
surrogates in conservation assessments. Taxonomic surrogates were the most used biodiversity
surrogates at all scales. Socioeconomic criteria were used in many conservation assessments. I argue
that 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. A
conservation 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 more
rapid and less expensive broader one, should be carefully considered. The study of Chapter 3 assessed
the complementarity between regional- and local-scale assessments and the implications on the choice
of biodiversity features at both scales. The study was undertaken in Réunion Island. A biodiversity
assessment was performed at a regional scale and measured against a finer-scale assessment
performed over a smaller planning domain. Two datasets composed of species distributions, habitat
patterns and spatial components of ecological and evolutionary processes were compiled as
biodiversity surrogates at each scale. Targets for local-scale processes were never met in regional
assessments, while threatened species and fragmented habitats were also usually missed. The regional
assessment targeting habitats represented a high proportion of local-scale species and habitats at target
level (67%). On the contrary, the one targeting species was the least effective. The results highlighted
that all three types of surrogates are necessary. They further suggested (i) that a spatial strategy based
on a complementary set of coarse filters for regional-scale assessments and fine filters for local-scale
ones can be an effective approach to systematic conservation assessments; and (ii) that information on
habitat transformation should help identify where efforts should be focused for the fine-scale mapping
of fine filters. Together with priority-area setting, the identification of threatened biodiversity features has
helped to prioritise conservation resources. In recent years, this type of assessment has been applied
more widely at ecosystem-level. Ecosystems can be categorised into critically endangered, endangered
and vulnerable, following the terminology of the IUCN Red List of threatened species. Various criteria
such as extent and rate of habitat loss, species diversity and habitat fragmentation can be used to
identify threatened ecosystems. An approach based only on the criterion of the quantification of
habitat loss was investigated in Chapter 4 for the Little Karoo, South Africa. Habitat loss within
ecosystem type is quantified on land cover information. The study analysed the sensitivity of the
categorisation process to ecosystem and land cover mapping, using different datasets of each. Three
ecosystem classifications and three land cover maps, of different spatial resolutions, were used to
produce nine assessments. The results of these assessments were inconsistent. The quantification of
habitat loss varied across land cover databases due to differences in their mapping accuracy. It was
reflected on the identification of threatened ecosystems of all three ecosystem classifications. Less
than 14% of extant areas were classified threatened with the coarsest land cover maps, in comparison
to 30% with the finest one; and less than 9% of ecosystem types were threatened with the coarsest land
cover maps, but between 15 and 23% were threatened with the finest one. Furthermore, the results
suggested that the identification of threatened ecosystems is more sensitive to the accuracy of habitat
loss quantification than the resolution of the ecosystem classification. Detailed land cover mapping
should be prioritised over detailed ecosystem maps for this exercise.
This thesis highlighted the importance of ecosystems and processes as biodiversity surrogates in
conservation 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 important
role of mapping habitat transformation for systematic conservation plans.
Description
Thesis (MSc (Conservation Ecology and Entomology)--Stellenbosch University, 2007.
Keywords
Biodiversity conservation, Systematic conservation planning, Biodiversity surrogates, Dissertations -- Conservation ecology and entomology, Theses -- Conservation ecology and entomology