Geographical interest in ecological resources can be traced back at least to the period of interest in regional identification at the turn of the present century, because plant and animal distributions are a basic component of the character and identity of different regions. The stability and survival of natural ecosystems in many environments are presently being threatened by exploitation of ecological resources, reduction if not wholesale removal of ecological habitats, and environmental pollution. This chapter focuses on the reasons for interest in ecological resources, and the various ways in which pressures are currently being placed on remaining ecological resources at several scales of study. The expansion of urban land into formerly rural environments, especially, has caused the removal of numerous ecological habitats and the disruption of large numbers and wide varieties of ecosystems.