The U.S. has more than 87,000 dams greater than six feet high (and two million overall). While many dams continue to provide benefits such as flood control, irrigation, and water supply, for other dams the cost of maintenance or the negative effects on communities, fish, and tribes justifies their removal.
Dam owners and regulators decide whether to remove a dam by weighing many factors including: the cost of removal and the ability to replace any lost power generation against avoided long-term maintenance; safety concerns; benefits to endangered fish populations; increased recreational and commercial fishing; and restoration of cultural values of nearby tribes.
By 2020, roughly 70% of dams will be more than 50 years old, inviting us to reconsider the value to the public of long-term investments in this infrastructure.
<u>ANSWER:</u>
The resources available for the population have decreased would have caused the change.
<u>EXPLANATION:</u>
- The carrying capacity of a population is the maximum size of population that a species can sustain in the environment using the available factors.
- When the carrying capacity of a population decreases, it means that the resources for the species are not available in enough quantity to allow the population to sustain and thrive.
- Insufficient food, space, light and water are major causes for a decrease in the "carrying capacity" of a population.
The difference is:
1. An ecoregion is an area that is known for its environmental conditions, landscapes, and soil
2. A region is an area that is part of a country or some parts of the world
The transport of material due to gravity.
I think you wanted to know whether the statement in question is true or false. Based on this assumption, i am answering the question. It is a true fact that the Danube River is navigable and thus connects many of the countries of the European continent. I hope that the answer has come to your help.