A landscape approach to reserving farm ponds for wintering bird refuges in Taoyuan, Taiwan

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Title: A landscape approach to reserving farm ponds for wintering bird refuges in Taoyuan, Taiwan
Author: Fang, Wei-Ta
Abstract: Man -made farm ponds are unique geographic features of the Taoyuan Tableland . Besides irrigation , they provide refuges for wintering birds . The issue at hand is that these features are disappearing and bring with it the loss of this refuge function . It is ecologically significant because one fifth of all the bird species in Taiwan find a home on these ponds . This study aims at characterizing the diversity of bird species associated with these ponds whose likelihood of survival was assessed along the gradient of land development intensities . Such characterization helps establish decision criteria needed for designating certain ponds for habitat preservation and developing their protection strategies . A holistic model was developed by incorporating logistic regression with error back -propagation into the paradigm of artificial neural networks (ANN ) . The model considers pond shape , size , neighboring farmlands , and developed areas in calculating parameters pertaining to their respective and interactive influences on avian diversity , among them the Shannon -Wiener diversity index (H ? ? ) . Results indicate that ponds with regular shape or the ones with larger size possess a strong positive correlation with H ? ? . Farm ponds adjacent to farmland benefited waterside bird diversity . On the other hand , urban development was shown to cause the reduction of farmland and pond numbers , which in turn reduced waterside bird diversity . By running the ANN model with four neurons , the resulting H ? ? index shows a good -fit prediction of bird diversity against pond size , shape , neighboring farmlands , and neighboring developed areas with a correlation coefficient (r ) of 0 .72 , in contrast to the results from a linear regression model (r < 0 .28 ) . Analysis of historical pond occurrence to the present showed that ponds with larger size and a long perimeter were less likely to disappear . Smaller ( < 0 .1 ha ) and more curvilinear ponds had a more drastic rate of disappearance . Based on this finding , a logistic regression was constructed to predict pond -loss likelihood in the future and to help identify ponds that should be protected . Overlaying results from ANN and form logistic regression enabled the creation of pond -diversity maps for these simulated scenarios of development intensities with respective to pond -loss trends and the corresponding dynamics of bird diversity .
URI: http : / /hdl .handle .net /1969 .1 /3984
Date: 2006-08-16

Citation

A landscape approach to reserving farm ponds for wintering bird refuges in Taoyuan, Taiwan. Available electronically from http : / /hdl .handle .net /1969 .1 /3984 .

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