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 In
urban regions around the world, improving the health and vigor
of urban forests can yield great economic and environmental
benefits for both today and tomorrow. From the street trees
in front of a downtown store to the large trees found in many
parks and greenways, the urban forest is a critical part of
the landscape.
Trees buffer the “wind
tunnels” created by buildings and streets, while adding
a living element to the concrete, steel, and glass. Trees shade
streets, sidewalks, and buildings to reduce the impact of the
sun’s rays and the buildup of urban heat. Trees release
water back into the air, working as natural air conditioning
systems. Trees reduce noise pollution by absorbing unpleasant
sounds such as those generated from traffic and construction.
Trees in the community filter dirt and chemicals from the
air.
In addition to improving air
quality, trees are valuable in protecting water quality.
Society’s existence depends on fresh, clean water from
rivers, streams and groundwater. Unfortunately, unhealthy
conditions are common in America’s streams and rivers today
due in part to the loss of forest cover.
Stream management has changed
in recent years, and restoring stream integrity is now one of
the nation’s highest conservation priorities. Formerly,
people thought that the way to manage streams was to rework
them into more efficient systems to hold and deliver water according
to people’s needs and desires. Rivers were dammed and great
levees were built to contain floods. Some rivers and streams
were cleared and straightened so water could run through faster,
and vegetation was often removed to allow farming and development
up to the streams’ edges. Where those efforts were
accomplished, the landscape was greatly altered, as people built
communities, irrigated deserts, and drained wetlands in areas
now protected from flooding. Where engineering projects failed,
however, the alterations often served to make flooding even
worse.
 Today’s
thinking about stream management focuses on understanding the
variable nature of a watershed and its streams and designing
management approaches that build upon and take advantage of
the stream’s inherent tendencies. Much of what needs
to be done to restore the stream’s integrity needs to happen
on the land around it.
The riparian area—that
area alongside the stream that connects the stream banks to
the surrounding uplands—is often the most important management
area. If it can be maintained in permanent grass or forest
cover, the protection afforded the stream increases significantly.
Riparian areas play several roles, but none are more crucial
than the trapping of soil and filtering of nutrients as they
wash down from the uplands. Caught in the riparian zone,
nutrients nourish the vegetation instead of adding to stream
pollution. Where trees grow on stream banks, strong root
systems help to provide stability and prevent the bank from
washing away. Less runoff and erosion allows more recharging
of the groundwater supply. Shade keeps water temperatures
cool to hold more dissolved oxygen, which is important for maintaining
freshwater fish. Leaves fall into the water, where they provide
food for aquatic insects and other organisms. Even when a stream
bank tree dies and falls into the stream, it forms an important
part of the stream structure as shelter and a source of food
for stream insects, fish and other animals. Thus, the trees
become an important part of maintaining healthy stream communities
that help maintain clean water.
Forested riparian buffers
are also critical wildlife habitat areas. Because of their
nearness to water, these buffers are the most biologically rich
areas on any landscape. Maintaining a healthy forest cover,
avoiding soil damage by careful machine operations, and controlled
use of any chemicals can ensure that we have highly productive
forests, clean water, and abundant wildlife.
Good land managers can maintain
the quality of streams and rivers and, where those streams and
rivers have been damaged in the past, restore watershed function.
Trees planted to help maintain stream stability can create a
long-term, environmental benefit for everyone who uses
water.
The gifts of trees are many.
Birds and insects will live and nest in its branches. Its roots
will penetrate deeply into the soil, building soil structure
and quality as they die and re-grow. The tree’s trunk will
thicken with wood that represents tons of carbon dioxide that
has been taken out of the air and placed into “carbon storage,”
where it is doing its part against the threat of global climate
change.
The rain will hit its leaves
and trickle gently to the ground to nourish the tree and the
other plant life under it, instead of pounding on unprotected
soil to create erosion and pollution. The air that moves through
its branches will be purified as pollutants are trapped on leaf
surfaces, chemicals are absorbed, and carbon dioxide is taken
in to provide a basic building block for the tree’s growth.
Give the generations that
follow you the gift of trees.
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