Environmental Pollution Simulation Review and Summary
1.2 How have environmental cycles changed?
The capacity of ecosystems to provide benefits to humans, that is to provide ecosystem services, derives from environmental cycles of water, nitrogen, carbon, and phosphorus. These processes have in some cases been significantly modified by human activity. Changes have been more rapid in the second half of the 20th century than at any other time in recorded human history.
Water cycle: Water withdrawals from rivers and lakes for irrigation, urban uses, and industrial applications doubled between 1960 and 2000. Globally, humans use slightly more than 10% of the available renewable freshwater supply. However, in some regions such as North Africa, groundwater is withdrawn at a faster pace than it is renewed. Carbon cycle: In the last two and a half centuries, the concentration of carbon dioxide in the atmosphere has increased by one third. Land ecosystems were a net source of carbon dioxide during the 19th and early 20th century and became a net carbon sink sometime around the middle of the last century. This reversal is due to increases in plant growth brought about by, for example, new forest management and agricultural practices. Nitrogen cycle: The total amount of nitrogen made available to organisms by human activities increased nine-fold between 1890 and 1990, especially since 1950 because of the use of synthetic fertilizers. Human activities are now responsible for as much nitrogen made available as all natural sources combined.
Phosphorus cycle: The use of phosphorus fertilizers and the rate of phosphorus accumulation in agricultural soils nearly tripled between 1960 and 1990, but has declined somewhat since. The flow of phosphorus into the oceans is now three times the natural flow.
This study is focused on stream and landscape modifications and their effects on interaction between two predatory fish: brown trout and walleye. Both species in the Au Sable River system make extensive long-range movements.
The capacity of ecosystems to provide benefits to humans, that is to provide ecosystem services, derives from environmental cycles of water, nitrogen, carbon, and phosphorus. These processes have in some cases been significantly modified by human activity. Changes have been more rapid in the second half of the 20th century than at any other time in recorded human history.
Water cycle: Water withdrawals from rivers and lakes for irrigation, urban uses, and industrial applications doubled between 1960 and 2000. Globally, humans use slightly more than 10% of the available renewable freshwater supply. However, in some regions such as North Africa, groundwater is withdrawn at a faster pace than it is renewed. Carbon cycle: In the last two and a half centuries, the concentration of carbon dioxide in the atmosphere has increased by one third. Land ecosystems were a net source of carbon dioxide during the 19th and early 20th century and became a net carbon sink sometime around the middle of the last century. This reversal is due to increases in plant growth brought about by, for example, new forest management and agricultural practices. Nitrogen cycle: The total amount of nitrogen made available to organisms by human activities increased nine-fold between 1890 and 1990, especially since 1950 because of the use of synthetic fertilizers. Human activities are now responsible for as much nitrogen made available as all natural sources combined.
Phosphorus cycle: The use of phosphorus fertilizers and the rate of phosphorus accumulation in agricultural soils nearly tripled between 1960 and 1990, but has declined somewhat since. The flow of phosphorus into the oceans is now three times the natural flow.
This study is focused on stream and landscape modifications and their effects on interaction between two predatory fish: brown trout and walleye. Both species in the Au Sable River system make extensive long-range movements.