In biology and ecology, the environment is all of the natural materials and living things, including sunlight . If those things are natural, it is a natural environment. Some people call themselves environmentalists . They think we must protect the natural environment, to keep it safe. Things in the natural environment that we value are called natural resources . For example; fish , sunlight, and forests . These are renewable resources because they come back naturally when we use them. Non-renewable resources are important things in the environment that are limited for example, ores and fossil fuels . Some things in the natural environment can kill people, such as lightning .