Road densities and species abundance

Roads form a complex system to connect people and goods. In recent years, the economic development and population increase have led to the active construction of new roads and railways. Therefore, as the human activities increase, the density of roads also escalates. However, new road construction affects many natural habitats and the many species reside and feed in them. Excessive increase in road density may cause habitat fragmentation and bring about detrimental impacts on the species living in the area, especially on small islands (a "small" island is one with an area less than 1,000 square kilometers or a population less than one million people). A small island is more vulnerable mainly because of its limited area. The imbalance and deterioration of the ecological environment caused by the construction of roads and railways are more severe and obvious on a small island than on a large continent. Habitats lost to new road construction are often unique and can not be easily compensated in other areas. The feeding behaviors and movement patterns of species may change in a negative way in response to the modification of habitats. Once species are forced out of their original habitat, they can face extinction in a few short years. This paper tries to address these issues by using GIS to calculate the areas and road densities of small islands (Kinmen, Penghu, the Green Island, and others) surrounding Taiwan and their species abundance. The number of species of resident birds is chosen as an indicator of biodiversity because of birds' greater sensitivity to changes in the environment. If the environment changes faster than they can adapt to it, they will be forced to leave the original habitat in search of a new one. Therefore, the number of species of resident birds in an area can serve as a measure of the soundness of the local environment. To assess the status of species abundance on each island examined, a biodiversity formula is used to calculate the theoretical number of resident bird species on each island and compare the number with the one recorded by actual sightings of bird watchers. Based on these data, this paper discusses the possible connections between road development and the reduction in biodiversity.