The word "ecology" was first used in 1866 by German scientist Ernst Heinrich Haeckel (1834-1919). A zoologist and proponent of Charles Darwin's theory of evolution, Haeckel was known for his speculative approach to natural history and his frequent invention of new scientific terms.
Ecology did not acquire much of its current meaning, however, until it was adopted several decades later by the Danish botanist Eugenius Warming (1841-1924). In his pioneering text on plant ecology, Plantesamfund (1895), Warming defined ecology as the study of "the manifold and complex relations subsisting between the plants and animals that form one community." Warming's book was later translated into other languages and appeared in English as Oecology of Plants; An Introduction to the Study of Plant Communities (1909).
Warming emphasized the environmental context in which plant communities are formed and the role of such factors as temperature, moisture, and soil composition in determining their expansion or decline. In Warming's description, plant communities are always in a state of change, with some species overtaking and replacing others as relationships between plants shift and as conditions outside the community are altered over time. Ultimately, the progressive succession of plant species leads to a climax plant community, with the final stage of development producing the hardiest and most adaptable forms of vegetation for a particular ecological area.