Natural environment
The natural environment, commonly referred to simply as the environment, is a terminology that comprises all living and non-living things that occur naturally on Earth or some region thereof. This term includes a few key components:
- Complete ecological units that function as natural systems without massive human intervention, including all vegetation, animals, microorganisms, rocks, atmosphere and natural phenomena that occur within their boundaries.
- Universal natural resources and physical phenomena that lack clear-cut boundaries, such as air, water, and climate, as well as energy, radiation, electric charge, and magnetism, not originating from human activity.
The natural environment is contrasted with the built environment, which comprises the areas and components that are strongly influenced by man. A geographical area is regarded as a natural environment (with an indefinite article), if the human impact on it is kept under a certain limited level (similar to section 1 above). This level depends on the specific context, and changes in different areas and contexts. The term wilderness, on the other hand, refers to areas without human intervention.

# Challenges
It is the common understanding of natural environment that underlies environmentalism  a broad political, social, and philosophical movement that advocates various actions and policies in the interest of protecting what nature remains in the natural environment, or restoring or expanding the role of nature in this environment.  While true wilderness is increasingly rare, wild nature (e.g., unmanaged forests, uncultivated grasslands, wildlife, wildflowers) can be found in many locations previously inhabited by humans.
Goals commonly expressed by environmental scientists include:
- reduction and clean up of pollution, with future goals of zero pollution;
- cleanly converting nonrecyclable materials into energy through direct combustion or after conversion into secondary fuels;
- reducing societal consumption of non-renewable fuels;
- development of alternative, green, low-carbon or renewable energy sources;
- conservation and sustainable use of scarce resources such as water, land, and air;
- protection of representative or unique or pristine ecosystems;
- preservation of threatened and endangered species extinction;
- the establishment of nature and biosphere reserves under various types of protection; and, most generally, the protection of biodiversity and ecosystems upon which all human and other life on earth depends.
Very large development projects - also called megaprojects - pose special challenges and risks to the natural environment. Major dams and power plants are cases in point. The challenge to the environment from such projects is growing because more and bigger megaprojects are being built, in developed and developing nations alike.
Recently, there has been a strong concern about climate change such as global warming caused by anthropogenic releases of greenhouse gases, most notably carbon dioxide, and their interactions with humans and the natural environment. Efforts here have focused on the  mitigation of greenhouse gases that are causing climatic changes (e.g. through the Climate Change Convention and the Kyoto Protocol), and on  developing adaptative strategies to assist species, ecosystems, humans, regions and nations in adjusting to the Effects of global warming.
A more profound challenge, however, is to identify the natural environmental dynamics in contrast to environmental changes not within natural variances. A common solution is to adapt a static view neglecting natural variances to exist. Methodologically this view could be defended when looking at processes which change slowly and short time series, while the problem arrives when fast processes turns essential in the object of the study.