Human activity has a great impact on the earth. It is not possible to know for sure the extent that human activity has altered natural ecosystems. Some human impacts are well understood and are a cause for concern.
Human Activity Impacting Soil
Roughly 50 percent of the earth's soils are directly impacted by humans. Human activity has reduced the amount of available nutrients in soil. Scientists are naming the current geological time period the anthropocene due to the extent that humans are influencing soil composition.
Human Activity Impacting Populations
Extinction of animal populations can be a result of human activity. It is often times the indirect effects of human activity that destroy habitat and endanger organismal populations. When humans alter the environment by converting land for development, commercial forestry, agriculture, and grazing, organisms living in those environments are impacted and may become endangered.
Grizzly bear (wilderness land area reduced in size)
Snail kite (marsh habitat drained)
Ringed sawback turtle (construction of reservoir that limited food supply)
Human Activity Impacting Water Composition
Humans can alter environmental water quality and composition through their actions. Fertilizer resulting from agriculture enter streams and waterbodies. Rather than fertilizing the plants they were intended too, fertilizers can cause massive aquatic plant growth that can completely alter ecosystems.
Human Activity Impacting Temperature
Since the industrial age, humankind has produced emissions of CO2 and methane gas. As these gases build up in the atmosphere they trap heat energy from the sun and produce a temperature rise on earth.