In addition, if we apply a truly ecological perspective, the social, hydrological, atmospheric, and built components of the systems must also be included. All the disciplines required for this complete ecological understanding of an urban area have not been pulled together in a focused study before. This is cutting edge research. Ecological changes and interactions take a long time to play out. This is because interactions often have to go through several steps, or have slow rates of change.
Many ecological processes take decades to act or to have obvious effects.
And on top of all that, the physical environment itself is changing around the ecosystems. LTER stands for Long-Term Ecological Research. It is a research program sponsored by the National Science Foundation that provides support for ecological studies and experiments that take longer to yield results than the normal grant, which lasts for only one to three years. The program was established in 1980. There are now 21 LTER sites in total.