|How can we protect endangered aquatic species that
are isolated by dams?
|Question Date: 2018-04-04|
That’s an important issue. As you probably know,
some fish species travel upstream to reproduce. If
they can’t get over the dam, that species is
probably doomed to extinction. One solution is
“fish ladders,” which are sort of like
stairs for fish. These are usually off to the side
of a dam and have water flowing over steps that
the fish can climb. Some research shows that fish
ladders are not very effective. One study showed
that only 3% of fish made it to their spawning
grounds. Some high mountain lakes are
artificially stocked be dropping hatchery-raised
fish out of helicopters.
One solution is to actually remove dams. There is
a growing trend to get rid of dams that are not
necessary. Some dams were created to provide
recreation. Others were used for power in the
past, but are no longer used or needed. Some were
built for flood control. Unfortunately, while dams
are helpful in preventing frequent, small floods,
they can actually cause massive floods if the dams
fail or the reservoirs get too full. Removing dams
can improve water quality, habitat, and other
forms of recreation. Dam removals are not popular
with people who had a house near a lake and now
have a house near a large mud puddle. The mud will
probably grow over into a meadow, and then a
forest over the coming years. But that may not
make the homeowners happy if they prefer a lake.
If you’re interested in issues like this, you
may want to study conservation biology.
Thanks for asking,
Producing energy usually involves tradeoffs, and
it’s often unclear what the best solution is.
Hydroelectric power sources, including dams,
have been described as more environmentally
friendly than fossil fuels because they produce
smaller amounts of pollutants. However,
recent research suggests that dams produce
significantly more greenhouse gases due to
decaying vegetation than was previously thought.
Furthermore, as you point out, dams change
local ecosystems and threaten local wildlife.
Dams trap sediment, changing the environment both
upstream and downstream of the dam, and prevent
fish from migrating.
Three ways in which the threat to wildlife can
be reduced are engineering systems of dams,
design changes to individual dams, and changing
operation procedures of dams. For a system of dams
on a river, some researchers have suggested that
slight reductions in the total number of dams may
greatly reduce the harm to fish populations while
maintaining most of the energy output. Individual
dams can be engineered to include bypass
channels to allow fish and sediment to pass
through. Other methods of moving fish across a
dam include fish ladders, elevators, and
cannons. Changes to dam operation include
fully opening dams in certain seasons to help
restore the native ecosystem, gradually changing
the flow of water through a dam rather than
abruptly changing flow in response to energy
needs, and the area upstream of dams can be
sluiced and flushed to move sediment downstream.
To effectively protect ecosystems, new dams should
be built and operated with these changes, and old
dams should be upgraded. This is a political
issue, as improvements to dams generally require
tax dollars. Ultimately, the environmental
impact of dams will be determined by how much
people are willing to pay to protect their
With difficulty, it appears. From the
information that I found all seems to be related
to the danger, not the protection. Here are the
first 2 hits I got:
"The construction of a dam on a river can block or
delay upstream fish migration and thus contribute
to the decline and even the extinction of species
that depend on longitudinal movements along the
stream continuum during certain phases of their
Implications of Dam Obstruction for Global
Freshwater Fish Diversity:
The article above is by CR Liermann - 2012 -
Cited by 186 - Related articles Jun 1, 2012 - A
synthesis of obstruction data and
fish traits indicates that taxa such as lampreys
(Lampetra spp.), eels (Anguilla spp.), and shads
(Alosa spp.) are at particular risk of species
loss. Threatened eco-regions with heavy dam
obstruction and above-average counts of total,
diadromous, or endemic species are found on all
Well, one simple way is simply to remove the dams.
Unfortunately that causes a host of other problems
that are not so simple. One way would be to move
the species around with human help, but that only
works for species that we humans know exist and
that we can move. In practice, it isn't easy.
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