A focus of environmental science not studied in ecology is the

The influence of human activities on the environment

Explanation:

Anthropogenic activities may have negative effects on the environment by declining its biodiversity and by reducing natural resources. Human activities affect the environment through the use of fossil fuels (greenhouse gases), by contributing to the pollution of extensive areas, by overpopulation, eutrophication, deforestation, etc. The most significant effects of anthropogenic activities include the loss of biodiversity, climate change (global warming), habitat fragmentation, environmental degradation (e.g., ocean acidification), the introduction of invasive species, species extinction, etc.