The limitation is not the availability of space, but the number of people in relation to resources and the capacity of earth systems to support human beings. Changes in technology can cause significant changes, either positive or negative, in carrying capacity. Water resources can limit the caring capacity of an area. Humans have developed means of meeting water demand to a certain extent, but the solutions may affect plants, animals and other humans. Studying past droughts and water management practices are necessary factors planners need to consider to make appropriate recommendations on population growth.
Natural ecosystems provide an array of basic processes that affect humans.
Those processes include maintenance of the quality of the atmosphere, generation of soils, control of the hydrological cycle, disposal of wastes, and recycling of nutrients. Humans are changing many of these basic processes, and the changes may be detrimental to humans. Dams reduce flooding but may force people, animals and farm land to be relocated or lost. Weather modification is an attempt at man to adapt the water cycle, however, creating precipitation in one area may reduce precipitation in other areas. Many factors influence environmental quality.