Exploring Climate Change in the Classroom

One of the most pressing issues facing estuaries today is climate change. Climate extensions help students understand why and how climate change is impacting estuaries, as well as ways students can help reduce the impacts of climate change.

How can the Climate Change Interactive help me?

To gain more information on climate change in estuaries use the three diagrams to learn why estuaries are vulnerable to climate change, some of the indicators of climate change in estuaries, as well as the impacts.

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Use the slide show to explore diagrams and supporting information to enhance student's understanding of climate change. Each diagram has a magnifying glass that contains additional information about climate change topics.

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Illustrated estuary diagram

Shallow Waters

The depth and location of an estuary affects and changes conditions such as temperature and number of organisms present. Shallow estuarine waters allow great temperature changes.

Upland and Coastal Factors

Estuaries are influenced by the amounts of seawater and fresh water flowing through them. The quantity of seawater in an estuary changes with the changing tides, and the quantity of fresh water flowing into an estuary increases and decreases with rainfall and snowmelt.

Coastal Development

Human activities, such as changes in land use, increased nutrient runoff, and other impacts, are transforming coastal ecosystems. With climate change, these impacts on ecosystems—and estuaries—will be intensified.

While climate change impacts vary regionally, coastal communities and estuaries are clearly on the front lines of climate change. Coastal ecosystems, especially estuaries, are particularly vulnerable to the impacts of global climate change for three major reasons:

  1. Estuaries are influenced by both upland and coastal environmental factors. Since estuaries are where two distinct bodies of water meet and mix, each body of water brings its own unique climate sensitivities, causing estuaries to have more climate impacts than many other ecosystems. For example, an estuary would feel the impact of both reduced water levels caused by a climate-related drought and climate-induced changes in ocean currents.
  2. Estuaries are highly productive ecosystems because they are shallow, nutrient-rich protected waters. However, shallow waters mean that estuaries do not have much of a buffer to absorb changes in the environment associated with climate change, such as sea level rise or changes in water temperature.
  3. Many estuaries are already experiencing the stresses of coastal development. The coastal lands of the contiguous U.S. represent 17 percent of the nation’s continental land area, yet they are inhabited by over half the U.S. population. Climate change will interact with existing stresses from coastal development, intensifying the negative impacts on estuaries.
Illustrated estuary diagram

Air Temperature

Changes in air temperature can affect the growth and reproduction of plants and animals; the rate of evaporation; relative humidity; wind speed and direction; and precipitation patterns.


Changes in precipitation can affect how much freshwater flows into an estuary. This is critical, since freshwater supplies an important source of dissolved oxygen and nutrients to an estuary.

Coastal Storms

Changes in the intensity of tropical storms and hurricanes can produce stronger peak winds, and produce increased rainfall over some areas. This increased intensity could alter bottom sediment dynamics, phytoplankton and fisheries populations; salinity and oxygen levels; and increase coastal flooding.

Freshwater Inflow

Changes in freshwater inflow can influence changes in water residence time, salinity, turbidity, and even nutrient delivery. Nutrients, especially nitrogen and phosphorus, are key indicators of water quality in estuaries and are needed for plants to grow and reproduce.

Water Temperature

Changes in the temperature of the water could affect algal production, which can affect the availability of light, oxygen, and carbon for estuary species. Dissolved oxygen is critical for the survival of animals and plants that live in the water.

Coastal Currents

Changes in coastal currents could affect the properties of estuary waters (in particular temperature and salinity), water levels along the coast and access to nutrients and food (like phytoplankton) for estuary species.

Sea Level

Sea level is not rising uniformly around the world. Where it is rising, sea level can inundate wetlands and other low-lying lands, erode beaches, intensify flooding, and increase the salinity of rivers, bays, and groundwater tables.

There are several environmental factors that drive estuaries that are expected to play a role in global climate change. These factors effectively work as signals of climate change in estuaries and include changes in water temperature, air temperature, precipitation, sea level, freshwater inflow (i.e. fresh water entering into estuaries and the associated nutrients from the land), coastal storms (i.e. changes to the intensity and frequency of storms) and coastal currents.

Coastal currents are intricately tied to winds, waves, and land formations. With climate change there may be an effect on coastal circulation due to changes in the distribution of heat in the atmosphere and the oceans. These changes would affect winds and currents that move along the nation’s coasts, changing the location, timing, and velocity of some major coastal currents. An increase or decrease in wind-driven upwelling of deeper ocean water could have important implications for the survival of particular estuary and marine life.

Illustrated estuary diagram


Estuaries have various habitat types that are home to diverse plants and animals. Climate change impacts on habitats could mean the destruction, modification or loss of some of these habitats.

Nutrient Cycling

Estuaries help to regulate concentrations of nutrients such as nitrogen and phosphorous. Climate change could alter the balance of nutrient cycling and lead to undesirable plant growths, such as blooms of phytoplankton, and rob the water of oxygen.

Water Quality

Water quality is an indicator of the health of an estuary. Climate change impacts on water quality can affect species distribution and composition, alter their reproductive rates, and we could likely see increased invasive species.

Manmade Infrastructure

Coastal communities will be greatly exposed to risk from increased storms; coastal erosion, coastal flooding and beach loss due to rising sea levels; landslides due to increased winter rainfall; and inundation.

Species Range

With climate change, animals and plants that can change their geographic range—the place where they live on earth—will have a competitive advantage over those that do not.

Food Web

Climate shifts will change not only the abundance and growth rates of species in estuarine and coastal environments, but likely result in a shift in the type of species present, with unknown consequences to the food web.

Coastal Economies

The continuing prosperity many coastal communities reap from transportation, fishing and tourism is clearly linked to the health of their estuaries. But, human activities, like nutrient loading, land-use changes, damming, among others, are transforming estuary ecosystems. Add climate change to these impacts and the impact on estuaries will be intensified.

Climate change and its associated impacts are being increasingly felt in coastal areas. The impacts range from changes in basic functions of an estuary to changes to the coastal communities relying on estuaries.

Both water quality and nutrient cycling within an estuary will likely see dramatic climate-driven impacts. For example, a decrease in precipitation could cause the salinity of the estuary to increase and change how nutrients are flushed from rivers into the estuary.

Biological communities of an estuary will also be impacted with local and regional changes in habitat, species range, and food web interactions. For example, a decrease in the amount of freshwater inflow and associated nutrients in the water could change the area a salt marsh covers, as well as change the abundance and types of plants that make up the salt marsh community. Climate-driven changes in an estuary system will also result in changes in the overall range of species, favoring some and driving others toward extinction.

The changes are also likely to impact human communities. For example, there are likely to be changes in coastal economies (i.e., fishing, shipping, and tourism). Increases in sea level, storm frequency, and coastal currents could result in flooding and erosion of man-made infrastructure, such as roads, airports, shoreline housing, and recreation areas.

Freshwater estuaries are expected to show a decline in water levels, as the Great Lakes are predicted to experience lower water levels overall with climate change. On the Great Lakes, the shipping industry will be highly impacted as these levels become lower, possibly leaving coastal infrastructure high and dry.

Although coastal communities will be impacted by climate change, we have the power to take actions to reduce climate change impacts and adapt to the impacts that we can’t avoid.