Ecology (from Greek: οἶκος, "house", or "environment"; -λογία, "study of") is the branch of biology which studies the interactions among organisms and their environment. Objects of study include interactions of organisms with each other and with abiotic components of their environment. Topics of interest include the biodiversity, distribution, biomass, and populations of organisms, as well as cooperation and competition within and between species. Ecosystems are dynamically interacting systems of organisms, the communities they make up, and the non-living components of their environment. Ecosystem processes, such as primary production, pedogenesis, nutrient cycling, and niche construction, regulate the flux of energy and matter through an environment. These processes are sustained by organisms with specific life history traits. Biodiversity means the varieties of species, genes, and ecosystems, enhances certain ecosystem services.
Forestry is the science and craft of creating, managing, using, conserving, and repairing forests, woodlands, and associated resources to meet desired goals, needs, and values for human and environment benefits. Forestry is practiced in plantations and natural stands. The science of forestry has elements that belong to the biological, physical, social, political and managerial sciences.
If we recognise that every ecosystem can also be viewed as a food web, we can think of it as a circular, interlacing nexus of plant animal relationships (rather than a stratified pyramid with man at the apex)... Each species, be it a form of bacteria or deer, is knitted together in a network of interdependence, however indirect the links may be.
Murray Bookchin, The Ecology of Freedom (1982).