Examining Floristic Boundaries between Garden Types at the Global Scale

Gardens represent important sources of goods and services for their owners. This functionality translates directly into the types of plants cultivated in a given garden, and terminology has been developed to distinguish each category of garden according to its purpose. The factors explaining the differentiation and distribution of gardens have not previously been explored at the global scale. In this study, the plant lists for 44 sets of gardens from around the world were analyzed to explore their taxonomic similarities and the factors shaping each garden. Several biophysical and socioeconomic variables were examined at the appropriate scale for their roles in garden species distribution. Physical and climatic factors (temperature, rainfall, potential evapotranspiration and distance between settlements) were found to be significantly related with species makeup; all of these factors were less important than GDP per person, a proxy for household income, which was determined to be the primary driver of garden composition. All of the studied socioeconomic factors, such as language similarity among settlements and population density, were significant drivers of species distribution. However, the present analysis omits a number of variables due to data unavailability, such as garden size and owner gender, which have been previously recognized as influences on garden plant composition. The genera cultivated in different gardens were found to be very different from each other, and the definitions of each type are hard to establish from these data alone. Finally, the implications of likely future income variations, such those caused by severe economic crisis, and global climate change on bio-cultural diversity and food security are discussed.