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Do Trees Help or Hurt?

NEW ORLEANS, Louisiana (Achieve3000, August 25,

2009). The U.S. Army Corps of Engineers (USACE) wants

all trees that grow within 15 feet of more than 14,000 miles

of U.S. levees to be chopped down. The agency is concerned

AP Photo/Kita Wright that tree roots could undermine the levees. These barriers are

designed to protect low-lying communities from floods.

Critics of the plan, however, argue that trees reinforce levees and should remain in place.

The USACE is responsible for reducing the risk of potential disasters in the U.S. It has
issued hundreds of letters to levee managers across the nation. The letters urged managers
to take steps to reduce the risk of levee failures and catastrophic floods like the ones that
occurred in New Orleans following Hurricane Katrina in 2005. The USACE instructed
levee managers to fill in animal burrows and replace soil that had been lost to erosion. They
also gave instructions to cut down "unwanted woody vegetation." Thousands of trees have
since been felled as levee managers carry out the USACE's request.

Meanwhile, many civil engineers, environmentalists, and citizens have protested the
USACE's instructions to remove trees. They insist that trees pose little or no risk to levees.
They say trees actually help stabilize the soil surrounding the barriers.

"The literature on the presence of vegetation indicates that it may actually strengthen a
levee," said Andrew Levesque. Levesque is a senior engineer for King County, Washington.
The USACE wants trees removed along six rivers in the county. These rivers are considered
vital to salmon populations.

Levesque is hesitant to remove the trees because they are a vital part of fragile river and
wetland ecosystems. Trees drop dead leaves into the water. The leaves attract insects, which
are a source of food for fish. Trees also provide shade. This creates cool refuges for fish
when other areas of the river become too warm.

Some non-USACE engineers also argue that trees do not cause levee failures.

"There's never been a documented problem with a tree," said George Sills. Sills formerly
worked for the USACE. Sills conducted analyses that he said "looked at the possibility that
the trees caused any of the [levee] failures in New Orleans." According to Sills, his research
"determined that trees did not lead to any of these failures."

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Officials at the USACE concede that they are unaware of a single instance when a tree was
directly to blame for a levee failure. However, they note that trees have been known to
cause dam failures. This includes a 1970s collapse in Georgia that claimed 39 lives.

"[The USACE has] decades of experience that says you shouldn't have trees on your
levees," said dam and levee expert Eric Halpin. Halpin currently serves as the agency's
special assistant for dam and levee safety.

According to the USACE, removing trees from levees protects the structures from damage
from roots. It also makes the barriers easier to inspect and repair during a flood.

"If you're going to have a levee, you have to be able to maintain [it] and make it safe," said
Larry Larson. Larson is executive director of a group that represents levee insurers and
engineers.

Despite USACE arguments for removing trees, the agency has compromised with some
communities. After months of negotiations, the USACE agreed to permit all but a few
dozen trees growing on the Ouachita River levee in Louisiana to remain. The agency also
abandoned plans to clear trees and other vegetation from 1,600 miles of levees in California.
State wildlife officials complained that the action would destroy habitat.

Other communities have not been so fortunate. In Portland, Oregon, residents lost a legal
battle to protect cottonwoods and poplars along the Columbia River. About 90 trees there
were cut down.

"[USACE engineers] don't care if that's good science," said Portland resident Walter
Valenta. "It is their policy."

The Associated Press contributed to this story.

Dictionary

catastrophic (adjective) causing massive destruction

negotiation (noun) the act of making a deal or an agreement

reinforce (verb) to support; to make stronger

stabilize (verb) to make or become steady and unlikely to change

undermine (verb) to gradually weaken something

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Related Links:

Learn more about the problem from the U.S. Army Corps of Engineers.
Learn more about the benefits of trees.

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Instructions:
Select the letter of the correct answer.

Question 1:
What is the cause and effect relationship that takes place in the article?

The USACE wants to cut down trees near levees because it is concerned that
tree roots will undermine the levees.
The USACE wants to fill in animal burrows near levees to prevent the growth
of "unwanted woody vegetation."
The USACE wants to build levees along six rivers in King County to protect
salmon populations there.
The USACE wants to cut down trees near levees because the trees drop dead
leaves into wetland ecosystems.

Question 2:
Which of these is a statement of opinion?

Many civil engineers, environmentalists, and citizens have protested the
USACE's instructions to remove trees.
The USACE abandoned plans to clear vegetation from 1,600 miles of levees
in California.
In Portland, Oregon, residents lost a legal battle with the USACE to keep
cottonwoods and poplars along the Columbia River.
Groups that successfully block the USACE's plan to cut down trees near
levees are putting public safety at risk.

Question 3:
Which is the closest synonym for the word catastrophic?

Industrious
Ruinous
Miraculous
Ferocious

Question 4:

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What is this article mainly about?
A debate regarding a USACE request to cut down trees that grow near U.S.
levees
The government's plans to reduce the risk of catastrophic flooding in the U.S.
A legal battle to protect cottonwoods and poplars along the Columbia River
The destruction that occurred in New Orleans following Hurricane Katrina

Question 5:
This article would be most useful as a source for a student research project on
__________.

Hurricane Katrina and its effect on New Orleans
Wetland ecosystems in the Pacific Northwest
Catastrophic dam failures and flooding
Government policy to prevent natural disasters

Question 6:
The article states:

These rivers are considered vital to salmon populations.

Which would be the closest synonym for the word vital?
Hostile
Neutral
Essential
Reliable

Question 7:
This article is placed in a category of news called "Environment." In which other
category would this article fit best?

Eye on People
Across the U.S.
Historical Events
World Beat

Question 8:
In the fifth paragraph, the author presents information about the role of trees in river
and wetland ecosystems in order to __________.

Provide support for the USACE's request that trees near levees be chopped
down

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Explain why Levesque is hesitant to remove trees along six King County
rivers

Describe how trees and other vegetation increase the presence of insects

Inform readers that many trees in King County are losing their leaves

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S ummarize the opposing opinions on the USACE's request to remove all trees that
grow near U.S. levees. Present the reasoning for both sides of the argument.
Explain which line of reasoning you consider to be stronger, and why.

Support your response with facts from the article, as well as ideas of your own.

Type your answer in the text box below.

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In your estimation, should trees growing within 15 feet of a levee be chopped down?

Yes
No

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