Spatial Distribution, Protected Area Coverage and Hotspot Analysis of Breeding Birds in Taiwan
Date Issued
2012
Date
2012
Author(s)
Wu, Tsai-Yu
Abstract
Although Taiwan is an important hotspot of avian endemism, efforts to use the available distributional information for conservation analyses have so far been incomplete. For the first time, a newly-assembled, large database of Taiwan’s breeding bird species has been used to apply recently developed statistical program to (1) model the distribution of Taiwan’s breeding bird species, (2) use these distribution to reassess the conservation status of these bird species, and (3) combine these models to determine hotspots of avian species richness.
I modeled the distribution of 116 out of 145 breeding bird species with five GIS-based distribution modeling techniques, namely multiple discriminant analysis (MDA), logistic regression (LR), genetic algorithm for rule-set production (GARP), ecological niche factor analysis (ENFA) and maximum-entropy (maxent). The resulting five distribution maps were then combined using an ensemble approach resulting in one “final map” for each species.
Each species’ coverage of the entire study area by these “final” modeled distributions was calculated. Each species was then placed into one of four quartiles, thus establishing a new measure of rarity called “range quartile rarity.” This measure thus distinguished 22 species with a limited distribution on mainland Taiwan.
I then also calculated how much of each species’ distribution was covered by Taiwan’s protected areas. Overall, 29.8% of the distributional ranges of the 116 modeled species are covered by protected areas. Using this newly available information on range quartile rarity and protected area coverage, I found that the conservation status of 71 species may need to be reassessed because possible conflicts exist between previously established and these newly established conservation-relevant measures.
Furthermore, these 116 distribution maps were used to generate hotspot maps using the following criteria: total species richness, endemic species richness, threatened species richness, and rare species richness. These hotspot maps were then used to determine the 5% most species rich grid cells (1) within the entire island of Taiwan and (2) within the entire island of Taiwan but outside of protected areas. Almost all the species richness and hotspot analyses reveal that the mountainous regions of Taiwan hold most of Taiwan’s avian biodiversity. The one substantial unprotected region which was consistently highlighted as an important avian hotspot is a large area of unprotected mountains in Taiwan’s north-east (Nan’ao mountainous region) which should become a high priority for future field work and conservation efforts. In contrast, other unprotected areas of high conservation value are just spatial extensions to areas already protected in the central and southern mountains. After combining the results of the four hotspot criteria, the Nan’ao mountainous region was found to be important again. Significant for conservation efforts is also the result that different hotspot criteria overlap only partially and sometimes hardly at all. Therefore, to protect areas based on only one hotspot criterion would not protected areas of other hotspot criteria in Taiwan.
The ensemble modeling approach was used on 116 out of the 145 breeding species because sufficient presence and absence data was available for these species. Because there is also an urgent need to build distribution models of the remaining bird species, which are mostly rare and cryptic species, a further data collection effort was made to assemble presence (but not absence) data for the remaining 29 species. This effort allowed the distribution modeling of another 27 breeding bird species of Taiwan using a statistical approach which has been proven to be especially reliable for modeling species with a low sample size of presence localities, namely the maximum entropy (Maxent) modeling technique. The newly available presence records were then used to model each species’ distribution. Detailed discussion of the interpretation and applicability of these distributions are provided, whereby close attention was paid to habitat requirements, the intactness and fragmentation of their habitat, the general detectability of the species and data reliability.
In summary, this study for the first time provides distributional maps using modern statistical distribution approaches for almost all of Taiwan’s breeding bird species. Such models are invaluable for pursuing macroecological and conservation related topics, such as conservation assessments of rarity and species richness hotspots. I used these models to investigate a few of the many possible topics which can be explored with these novel techniques. Many of my results are new and relevant for the conservation of Taiwan’s avifauna. Therefore, range quartile rarity and protected area coverage should be incorporated into future assessments of the conservation status of Taiwanese birds. Rare and cryptic species need increased monitoring efforts and improved censusing techniques. Short-term conservation efforts should focus on protecting those species-rich hotspots which are still unprotected as highlighted in this study. Future studies should add other taxa to the analyses as well as consider complementarity analyses and future land-use and climate change effects.
Subjects
biodiversity
conservation priorities
conservation status
distribution modeling
protected areas coverage
rarity
Taiwan avifauna
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-101-D92B44002-1.pdf
Size
23.32 KB
Format
Adobe PDF
Checksum
(MD5):01bc2191fab2cb4b59e39d83d9f5f322