Assessing Impacts of Highway Construction by Biodiversity Analyst
In this fast developing world, biodiversity is an increasingly important concept that can represent the overall condition of the ecosystem in a certain area. An area with high biodiversity indicates that it is the home of various organisms, which is normally located in the transition zone of two ecosystems. And these areas not only should be conserved because of the high value of scientific research but also because they provide important ecosystem services for other creatures.
Many factors will result in the loss of biodiversity. A well-known acronym proposed by the biologist, E. O. Wilson, is HIPPO, which stands for Habitat destruction, Invasive species, Pollution, human over-Population and Over-harvesting. Some researchers believe that the most important factor is habitat destruction, which will permanently destroy or displace organisms from a region and lead to an irreversible loss of biodiversity.
Formed by long, broad, and flat beaches, the western coast of Taiwan is a habitat for many endangered water birds: black-faced spoonbills and Chinese egrets and also has high biodiversity. Unfortunately, an important highway: West Coast Expressway has been planned to cross the heart of this area: Changhua County. To avoid severe habitat destruction and the following loss of biodiversity, the Directorate General of Highways of Taiwan authorized Taiwan Development Institute to measure the impact on biodiversity during the construction.
As stated in the scenario, Taiwan Development Institute must conduct a comprehensive spatial analysis and impact assessment to help Directorate of Highways making a smarter decision during and after the construction of highway. For measuring the impact on local biodiversity, several spatial analyses and biodiversity indices of water birds must be calculated, such as Shannon Index, Simpson Index, and Evenness Index.
In order to conduct spatial analyses and calculate various biodiversity indices appropriately, Taiwan Development Institute selected SuperGIS Desktop, Spatial Analyst, and the unique extension- Biodiversity Analyst to finish this research project.
First, a one-year on-site bird observation should be carried and used as the data sources for further analysis. The frequency of on-site observation is four times a month, and the duration of each observation is at least three days. The location where birds appeared was recorded and plotted on digital maps. At the same time, the research area was segmented into several small-scale habitats and then categorized into fifteen different types. And for the convenience of following analyses, 200m*200m grids are established in the study area.
Fig.1 The study area is located at the seashore of Changhua County.
After data preparation is completed, researchers had conducted several spatial analyses, including Average Nearest Neighbor, Hot Spot Analysis, and Density Analysis. The first one is used for identifying whether the birds appeared randomly in the whole study area. And the Hot Spot Analysis is executed for detecting the exact places where birds appeared abnormally. Finally, the density analysis is conducted for calculating the average bird density of each small-scale habitat.
And at last, to evaluate the difference of the bird amount and bird types between years, researchers selected Shannon Index, Simpson Index, and also the Evenness Index in this project. Since the above spatial Analyses and Indices are supported by SuperGIS Desktop and its Biodiversity Analyst extension, researchers of Taiwan Development Institute could operate it step by step to obtain the result of each analysis.
Fig.2 The number of bird types appeared in each grid (left) and the classification of habitats(right)
The result of this study shows that amount and total types of water birds have great variation between different months and are deeply influenced by the bird migration. Normally, the amount and types reached the peak in the autumn and winter. There is no significant difference in these numbers while comparing the condition before and after the highway construction. The biodiversity indices showed that there are abundant water birds resided in the study (Simpson index is very close to 1) and distributed evenly (Evenness index is approximately to 0.7) across the entire zone. The result of spatial analyses displayed that the most favorable habitat of water birds is the intertidal zone, followed by fishponds and wetlands. And the bird density of the whole study area is 75.83 per hectare, while the highest density is found in wetlands (754 per hectare).
Finally, this impact assessment report suggested that the construction of highway will make no severe loss of biodiversity in the study area. But it also advised the Directorate of Highways to avoid using certain heavy machines during autumn and winter. This suggestion ensured that the noise will not disturb the migration of most water birds, especially some protected species.
By using SuperGIS Desktop, Spatial Analyst, and the distinguished Biodiversity Analyst, various environmental impact assessments could be easily accomplished. SuperGIS Desktop and Spatial Analyst provide abundant capabilities that help users to execute various spatial analyses. Other than these two products, the Biodiversity Analyst offers extra convenience for various environmental studies, enabling users to calculate various indices for both point and polygon layers, like species richness (Margalef and Menhinick), evenness (Pielou), and diversity (Shannon, Simpson, Berger, etc.). With these SuperGIS products, scholars and environmental consultants can complete projects without spending a lot time and energy. And also, the completed assessment reports can assist the unit for construction make more insightful decisions and minimize the impacts.