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Investigating spatial relationships between biodiversity & wilderness:
a global scale study
Crewenna Dymond, Steve Carver
& Oliver Phillips
School of Geography, University of Leeds, Leeds, UK
e-mail: [email protected]
Method
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.
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.
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.
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.
Conceptual model of biodiversity-wilderness interactions
Solar energy
Aspect
Soil
Ocean currents
Figure.1
A key feature of this research has been the maintenance of consistency between data from
different sources. Data falls into several different categories:
Biological data
Wilderness data
Potential biodiversity
Climatic data
Geographic data
Latitude Altitude Evapotranspiration Precipitation Temperature
Population
Density
- species richness - birds, mammals, flowering plants and conifers
(Groombridge, 1994)
a) wilderness reconnaissance work of McCloskey & Spalding (1989)
b) global wilderness continuum from World Conservation and
Monitoring Centre and Lesslie (2000)
- precipitation, temperature and evapotranspiration from GRID
- 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
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.
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.
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.
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.
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