Human ecology is the interaction between humans and their environment, particularly the living ecosystems on which human life depends. An ecosystem is all the living organisms in a habitat, such as the fish and algae in a pond or the trees and earthworms in a forest, and the physical factors that support and affect them, such as sunlight and precipitation. Humans collect or grow food and fuel resources from Earth's ecosystems and are part of the Earth's food chains, where plants fix energy via photosynthesis, then animal herbivores consume the plants, and animal predators consume the herbivores. In the wake of global industrialization and a great increase in human population size, people are having an ever greater impact on the function and structure of the Earth's ecosystems. Humans are clearing much of the world's forest land, damming many of the world's rivers, and managing a majority of the Earth's most productive soils for agriculture.

Although science and engineering can develop new technologies that damage the environment, scientific research can conversely provide new environmentally friendly technologies for controlling pollution, collecting energy, and improving crop yields. Scientists studying ecosystems guide human interactions with the environment by documenting and monitoring human-initiated disturbances that result from, for example, the harvesting of timber, the catching of fish, or the building of cities, and they test new methods of restoring damaged ecosystems.

The world's religions also encourage human respect and care for ecosystems by providing explanations for natural phenomena and by discouraging destructive human activities and attitudes. The myths of Pacific Northwest Indians, for example, describe the cycle of salmon returning from the sea to spawn in rivers. The First Fish ceremony, held at the beginning of the salmon runs, temporarily halts all salmon harvest, thereby allowing some fish to escape and lay their eggs. Religious rituals or teachings can guide planting times and soil-conserving fallow on farm fields. Some Christian and Jewish farmers follow biblical instructions to provide a Sabbath year for the land to allow the soil to recover from crops. Islamic law provides guidance in managing wells, irrigation, and grazing lands. Religion may also protect the environment by discouraging greed and waste, and by encouraging respect for all creatures. The Jewish law found in the Torah, for example, prohibits wanton destruction of natural features, such as trees. Buddhists carefully replace insects and worms disturbed by plowing agricultural fields.

Religions may also designate ecosystems or species as sacred or provide them with special status, thus reducing over-harvest and conserving ecosystem components, such as predators. Native Hawaiian religion, for example, identifies some large sharks as family deities, thereby prohibiting their capture. Australian aborigines learn to respect plants and animals by adopting them as clan totems. Christian Ethiopian monks allow wildlife to remain undisturbed on their monastic grounds. Many religions identify scared trees or groves that may not be cut, or holy springs or rivers that may not be polluted.

Although they are frequently portrayed as opposites, both science and religion guide human environmental decision-making by identifying the best management alternatives, and encouraging human respect for, care of, and right relationship with the Earth's ecosystems.

See also BIOLOGICAL DIVERSITY; CHRISTIANITY, HISTORY OF SCIENCE AND RELIGION; ECOFEMINISM; ECOLOGY, ETHICS OF; ECOLOGY, RELIGIOUS AND PHILOSOPHICAL ASPECTS; ECOLOGY, SCIENCE OF; ECOTHEOLOGY; ISLAM, CONTEMPORARY ISSUES IN SCIENCE AND RELIGION; JUDAISM, CONTEMPORARY ISSUES IN SCIENCE AND RELIGION

SUSAN POWERS BRATTON