oxygen squeeze.” When water temperatures rise, these fish
seek refuge in the cooler temperatures of deeper water, but
if they encounter low levels of dissolved oxygen there, they
get “squeezed” into relatively small layers of suitable habitat.
Hot and crowded, scientists report that these stressed fish
become more susceptible to disease.
Increases in water temperature can also affect the
distribution of aquatic species. For instance, eelgrass is at the
southern end of its range here, and it’s already stressed by
high temperatures. Hot summers like those in 2005 and 2010
caused massive die-offs of this critically important habitat
for fish and crabs in the lower Bay. Scientists worry that
this species of underwater grass may eventually disappear
from the Chesapeake Bay as it retreats northward to more
Upstream, warming waters also threaten cold-water species
like brook trout. A fifteen-year study of factors affecting
population levels of Eastern brook trout showed that high
summer temperatures have a large influence, mostly by
decreasing survival of the youngest age classes. In another
study, U.S. Forest Service scientists found that that the
combination of warm waters and the presence of the nonnative brown trout limited the distribution of brook trout
But what about other Bay residents, like us? Hotter summers
mean more advisories when the combination of heat and
humidity create conditions where heat stress and heat-related illnesses become possible. Simultaneously, air-quality alerts signal when pollution concentrations may be
unhealthy for sensitive people. Soaring temperatures can
also threaten our way of life. For example, a recent study by
Penn State scientists found that climate change may pose a
threat to the dairy industry in Lancaster County, one of the
top milk-producing counties in the country, because hot
summer temperatures reduce yields of corn, a major feed
for dairy cows.
Mark Twain once wryly observed that, “Everybody talks
about the weather, but nobody does anything about it.”
It turns out that we have been, without meaning to do so.
The challenge we face now is what to do about these
Beth McGee, Ph.D., CBF’s Director of
Science and Agricultural Policy, worked for
federal and state environmental agencies
before joining CBF in 2003.
How are we making a difference?
CBF’s primary mission of saving the Bay and
mitigating climate change are inextricably
linked. And many of the solutions are the same.
Implementing the Chesapeake Clean Water
Blueprint will benefit the Bay and its rivers and
streams while also reducing greenhouse gases.
Here’s what you can do to help:
* Plant trees near your home to provide shade
in the summer.
* Carpool, bike, or use mass transit when
* Support the Chesapeake Clean Water
Blueprint. Visit cbf.org/blueprint to
From 1960 until 2014, EPA water
testing stations have monitored stream
temperatures, which appear to be
increasing across the watershed overall.
– 1 to 1
+ 1 to + 2
+ 2 to + 4
> + 4
DATA SOURCE: U. S.
SAVE THE BAY 17