Explore these topics:

• Human Use and Misuse
  • Fire Suppression
  • Stormwater Runoff
  • Structural Changes in Stream Channels
• You Can Make a Difference!

Human Use and Misuse

People often use parks in urban and suburban areas in a wide variety of ways: hiking, dog walking, running, mountain biking, horseback riding, driving, and playing sports including golf, tennis, and soccer.

In addition, people may misuse the park, by creating unauthorized trails, littering or dumping trash, allowing dogs off leash, not picking up after their dogs, vandalizing park property, and encroaching on its boundaries.

Streams in urban and suburban parks are subject to demands as well, because they often drain areas covered by buildings, streets and parking lots.

All of these demands, including the following, can create ecological threats to the natural communities in a park:

• Roads, buildings, and recreational facilities can fragment habitat.
• Animals may be killed on roads in the park.
• People traveling through the park by car, bike, horse, or foot can unintentionally spread weed seeds and/or insect pests and plant diseases on their shoes, clothes, or tires. Pet dogs, especially unleashed dogs, can also spread seeds, pests or diseases on their paws and fur.
• People and their pets can erode hillsides and trample plants when straying from trails.
• Motorized traffic creates air pollution that can harm plants and animals.
• Suppressing fire to protect nearby human property may change the mix of plant species in natural communities that have regularly experienced wildfires in the past.
• Urban stormwater runoff creates a number of problems, including flooding, erosion, water pollution, and increased turbidity.
• Dams, fords, water diversions, storm sewers, and sanitary sewer lines degrade habitat available to aquatic plants and animals.

Let’s look at a few of these in more detail.

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Fire Suppression

In the past, fires started by lightning burned until they ran out of fuel or were extinguished by rain. In addition, Native Americans periodically burned forests to clear underbrush in preparation for farming or hunting.

Many natural communities are adapted to fire and may even depend on fire. Plants that can survive repeated fires have certain characteristics, such as thick bark or the ability to resprout from their roots. Some pine cones, covered in resin, actually need the heat of fire to melt the resin and release seeds—and when the seeds are released, they land on freshly groomed (burned) sunlit forest floor.

For decades, fire has been suppressed in many parks to protect human lives and property. Fire suppression changes natural communities by allowing species that aren’t fire-adapted to move into natural communities once populated predominantly by fire-adapted species.

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Stormwater Runoff

In urban and suburban areas, paved and developed surfaces prevents rainwater from soaking into the ground. Instead, rainwater quickly runs into storm drains, which carry it directly to the nearest stream.

Here are some of the problems caused by stormwater runoff in urban and suburban areas:

• Stormwater runoff increases flooding
• Stormwater runoff increases water pollution
• Stormwater runoff decreases available groundwater
• Stormwater runoff increases erosion in stream channels
• Stormwater runoff increases turbidity

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Structural Changes to Stream Channels

Stream channels continuously change through the natural processes of erosion, deposition, and flooding. In streams in and around urban and suburban areas, these natural processes may be hindered by dams, fords, riprap along stream banks, concrete channels, or diversion of the stream into underground pipes.

• Dams and fords
• Riprap
• Concrete channels
• Diverting streams underground

Streams that have been subjected to riprap, channelization, or diversion lose the ability to meander across the floodplain. This loss is detrimental to natural communities on the floodplain, whose soil nutrients are normally replenished by sediment that is eroded by floodwaters in one area and deposited on the floodplain elsewhere.

Depending on what structural changes have been made, modified streams may flood less often. When flooding becomes less frequent and groundwater isn't replenished, the floodplain dries out and non-flood tolerant plant species can encroach into a natural community of flood-tolerant species.

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You Can Make a Difference!

You can help by contacting a park near you to see if there are volunteer opportunities to help pick up litter, maintain existing trails and facilities, or educate park visitors about responsible land and water use. Another useful project is to work with your city to label stormwater drains with the message that the drains lead directly to the nearest creek and not to a water treatment facility.

You can also help by making changes on your property to reduce stormwater runoff. Ecobit: Is Your Property Watershed Friendly?

At a community level, street cleaning programs and strict enforcement of erosion control at construction sites help reduce the amount of sediment and pollutants going into stormwater drains.

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