Regional variation in habitat-occupancy thresholds: a warning for conservation planning

Rhodes, Jonathan R., Callaghan, John G., McAlpine, Clive A., de Jong, Carol, Bowen, Michiala E., Mitchell, David L., Lunney, Daniel and Possingham, Hugh P. (2008) Regional variation in habitat-occupancy thresholds: a warning for conservation planning. Journal of Applied Ecology, 45 2: 549-557. doi:10.1111/j.1365-2664.2007.01407.x


Author Rhodes, Jonathan R.
Callaghan, John G.
McAlpine, Clive A.
de Jong, Carol
Bowen, Michiala E.
Mitchell, David L.
Lunney, Daniel
Possingham, Hugh P.
Title Regional variation in habitat-occupancy thresholds: a warning for conservation planning
Journal name Journal of Applied Ecology   Check publisher's open access policy
ISSN 0021-8901
1365-2654
1365-2664
Publication date 2008-04-01
Year available 2008
Sub-type Article (original research)
DOI 10.1111/j.1365-2664.2007.01407.x
Open Access Status DOI
Volume 45
Issue 2
Start page 549
End page 557
Total pages 7
Editor Gillian Kerby
Place of publication Oxford, U.K.
Publisher Wiley-Blackwell
Language eng
Subject C1
0501 Ecological Applications
9608 Flora, Fauna and Biodiversity
Abstract 1. An important target for conservation planning is the minimum amount of habitat needed in a landscape to ensure the persistence of a species. Appropriate targets can be determined by identifying thresholds in the amount of habitat, below which persistence, abundance or occupancy declines rapidly. Although some studies have identified habitat thresholds, we currently have little understanding of the extent to which thresholds vary spatially. This is important for establishing whether we can apply the same planning targets across broad geographical regions.
Formatted abstract
1. An important target for conservation planning is the minimum amount of habitat needed in a landscape to ensure the persistence of a species. Appropriate targets can be determined by identifying thresholds in the amount of habitat, below which persistence, abundance or occupancy declines rapidly. Although some studies have identified habitat thresholds, we currently have little understanding of the extent to which thresholds vary spatially. This is important for establishing whether we can apply the same planning targets across broad geographical regions.

2. We quantified habitat–occupancy relationships for the koala Phascolarctos cinereus (Goldfuss) in three study regions that span much of its geographical range. Standard and piecewise (broken-stick/segmented) logistic regression were used to model linear and threshold habitat–occupancy relationships. We then used an information-theoretic approach to test: (1) whether habitat–occupancy relationships were described better by threshold or linear models and (2) where threshold models were better, whether, and to what extent, threshold points varied among study regions.

3. There was substantially greater support for the threshold than the linear models across a range of habitat qualities and landscape extents. The threshold models generally predicted a rapid decline in occupancy below the threshold points.

4. Estimated threshold points varied, sometimes substantially, among study regions. This may relate to cross-regional differences in habitat quality, demographic rates, and land-use patterns. The role of habitat fragmentation is unclear.

5. Synthesis and applications. Variation in threshold points among study regions suggests that we should be wary of using thresholds derived in one region for setting conservation planning targets in another. Rather, we should aim to set specific targets for individual locations (and species), while acknowledging the inherent uncertainties in these targets. This has implications for our ability to make general conservation prescriptions for widely distributed species. Future research should aim to develop generic models capable of predicting threshold responses across different landscapes and life-history characteristics.
Keyword broken-stick regression
extinction
habitat loss
koala
landscape ecology
logistic regression
Phascolarctos cinereus
piecewise regression
segmented regression
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

 
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Created: Fri, 03 Apr 2009, 21:01:27 EST by Helen Smith on behalf of School of Geography, Planning & Env Management