Challenges to Ecosystems Restoration

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Clip Guide

: Here you will find clear descriptions of what you just saw, how they know what they said they knew, why they know it to be trustworthy information. Finally we will ask the question, "So what!" and explore why the information is important.

WHAT do we know?

In this clip from the 2003 presentation “California Hydroclimate, CALFED and EWA,” USGS Project Director Larry Smith describes challenges facing watershed health in California.  Examples he includes are: the presence of mercury and increased sediment loads from mining, loss of wetlands to urban development, loss of salmon habitat, the introduction of invasive species, use of pesticides, and accumulation of selenium.

HOW do we know?

Individuals and organizations charged with water management, such as the US Geological Survey (where Mr. Smith was employed at the time of this clip), use multiple sources of information to assess the health of a watershed. They may make current observations, such as seeing erosion from a mine muddy water or taking measurements of the amount of selenium found in fish. They also use historic data to compare current and past fish populations or land use.

WHY can this be trusted?

Because the health of a watershed impact human health as well, water quality and availability tend to be well documented. As a result, scientists and public employees, like Mr. Smith, can compare the results of multiple research studies in order to make certain that their observations fit logically with current understanding of how their watershed functions.


The presence and quality of water are essential to life, industry, agriculture, and ecosystem survival. Yet water availability and health can easily be altered. As Mr. Smith describes, human activities can lead to increased amounts of sediment, toxic metals, or even new species in a watershed. The introduction of any of these components can contribute to ecosystem changes, die-off of species formerly found in the watershed, and threats to human health. Projects directors such as Mr. Smith research these changes and offer the local government and the public information about how such threats can be mitigated.


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