According to Campbell and Reece (2007) biogeography is the study of the past and present distribution of species. Cristopherson (1994) states that it is the study of the distribution of plants, animals and related ecosystems and geographical relationships with related environments over time. It involves a wide range of disciplines such as biology, geology, geography and ecology. The question arises: why are there so many more species in tropical rainforests than in woodlands? What allows a species to live in one area and prevents it from dispersing and colonizing in other areas? Biodiversity depends on many factors and large differences in wildlife species occur between different countries. This essay focuses on comparing and contrasting organisms found in Sea Point Co. Dublin, Glandalough, Co. Wicklow and Bolonia, Spain. Numerous organisms have been found in one country but not the other, such as the Mantodea (praying mantis) which was present in Spain but not in Ireland. Species abundance varied significantly, as can be seen in stoneflies (midges), which had higher numbers in Ireland than in Bolonia. There are many reasons for the differences between Irish and Spanish marine, terrestrial and freshwater fauna, both biotic and abiotic. Factors such as relationships between fauna, sunlight, temperature, water chemistry and soil will all be analyzed in the following paragraphs as they play an important role in the survival and distribution of species. When comparing the terrestrial fauna found in Bolonia and the glacial valley of Glendalough, many differences were noted. This part of the trip was carried out in the Bolonia matorall, a biome found in mid-latitude coastal regions (Campbell, 2011). ...... middle of paper ...... terrestrial invertebrates sampled in Spain had low agricultural input, cork oaks can grow and are only harvested in 10 year cycles, this low intensity harvesting leads to greater diversity. There are many reasons for the different diversity and abundance of species between two countries, and I think I have touched on the most important aspects of all. It seems that Spain's proximity to the equator is the driving force behind the high number of species, but since all organisms are different and prefer different habitats and environments, there are also many problems in comparing and analyzing the data. In this time of climate change, everything we know about species diversity may change and so studies like this are very important to understand how changing global temperatures and melting ice sheets affect organisms living on this planet..