Investigating spatial relationships between biodiversity & wilderness: a global scale study

1. Investigating spatial relationships between biodiversity & wilderness: a global scale study Crewenna Dymond, Steve Carver School of Geography, University of Leeds, Leeds, UK & Oliver Phillips e-mail: c.dymond@geog.leeds.ac.uk Method Natural phenomena do not operate within political boundaries. However, a shortage of extensive grid-based biological information makes it necessary to perform analysis on a country-by-country basis. The flow chart below summarizes the stages undertaken to investigate the validity of the hypotheses. Introduction Visualisation of the global distributions of biodiversity and wilderness suggests an interesting spatial pattern. This research aims to demonstrate how biodiversity (measured as the number of species per unit area or species richness) and wilderness quality might be related spatially at this scale. This has been achieved through the development of a conceptual model and statistical analysis of related physical and climatic factors. Conceptual model & hypotheses This work focuses on variables through which species richness and wilderness interact. The conceptual model below summarizes the physical and climatic factors that are thought to effect distributions of biodiversity and wilderness. Factors which are thought to contribute to wilderness, such as remoteness and naturalness are not influenced by country area. However, Figure 2 demonstrates that wilderness proportion does increase with unit area to a degree. Figure.1 Figure. 2 If biodiversity and wilderness are promoted by opposing forces then a decrease in species richness would be expected with an increase in wilderness proportion. To analyze how flowering plant species richness might be related to wilderness, it was first necessary to use the residuals from the species:area regression to establish the degree to which richness is higher than expected per area. A negative correlation was indeed found between these residuals and wilderness (r = -0.382, p = 0.01), consistent with this hypothesis. Climate has been identified as an important contributor to both wilderness and biodiversity. Indeed, flowering plants have a strong correlation with actual evapotranspiration (AET) (r = 0.589, p - 0.00). However, AET was poorly correlated with wilderness area (r = -0.118, p = 0.00) suggesting the second hypothesis concerning aridity as a wilderness driver should be rejected. Conceptual model of biodiversity-wilderness interactions A keyfeature of this research has been the maintenance of consistency between data from different sources. Data falls into several different categories: Biological data - species richness - birds, mammals, flowering plants and conifers (Groombridge, 1994) Wilderness data a) wilderness reconnaissance work of McCloskey & Spalding (1989) b) global wilderness continuum from World Conservation and Monitoring Centre and Lesslie (2000) Climatic data - precipitation, temperature and evapotranspiration from GRID Geographic data - latitude, altitude and population, generated in GIS or sourced through the School of Geography. The maps below show four examples of the data after cleaning. Results Analysis of the relationships between biodiversity, wilderness and environment has produced results of a numerical nature. It is possible to demonstrate the direction of these through the use of flowering plants as an example. Ecological literature accepts a linear relationship between species richness and area. Figure 1 indicates that this relationship operates at the global scale. A linear relationship between wilderness and area is not so intuitive. Solar energy Aspect Soil Ocean currents Potential biodiversity Latitude Altitude Evapotranspiration Precipitation Temperature Population Density Conclusion This research suggests that species richness:area and wilderness:area relationships exist at the global scale. It is proposed that a number of environmental factors are responsible for the global distribution of both biodiversity and wilderness. Statistical analysis, whilst clarifying some relationships, has highlighted the complexity of the problem. Some scale or geographical problems have also served to mask these relationships. For example, countries with a high latitudinal range have made it hard to confirm the hypothesis that wilderness proportion increases with latitude. It is anticipated that re-analysis at the temperate and tropical scales will produce more conclusive evidence for these relationships. Potential wilderness Remoteness Naturalness • Predictions can be made about the relationship between wilderness quality and species richness. For example, at the global scale this model predicts a negative relationship between wilderness and biodiversity. Additionally, latitude, altitude, population and climate (precipitation, temperature and evapotranspiration) are identified as key contributory factors. After synthesis of the literature and understanding of the model it is possible to hypothesize that: • wilderness is restricted to high latitudes whereas high species richness is located at low latitudes • wilderness is confined to dry environments whereas moist environments facilitate the development of high species richness • wilderness is restricted to high altitudes whereas species are more concentrated at low to moderate elevations. References Ahn, C.H. & Tateishi, R., 1994, Development of a global 30 minute grid potential evapotranspiration data set, Journal of the Japan Society Photogrammetry Remote Sensing, 33, 3, p 12-21 Groombridge, B. (Ed), 1994, Biodiversity Data Sourcebook, WCMC Biodiversity Series, no. 1, World Conservation Press Lesslie, R., personal communication, July 2000 McCloskey, M.J. & Spalding, H., 1989, A reconnaissance-level inventory of the amount of wilderness remaining in the world, Ambio, 18, 4, 221-227 Skellern, A., personal communication, May 2000 WCMC, 2000, World wilderness continuum, unpublished data