Monday, August 22, 2011

Protecting fragile vegetation at Hawksnest

The soil's surface... is the living skin of the earth.

When vegetation is destroyed, erosion creates a wound--as dangerous to the ecosystem as a festering sore.  In the resulting scars, invasive plants and animals can become established.

Healthy soil stores nutrients for plants--but with erosion, phosphorus escapes, creating imbalances in waterways downstream.

If erosion is allowed to continue unchecked, the resulting gullies will be very expensive to repair.  At Walden Pond State Reservation near Boston, erosion that went unchecked for decades cost over a million dollars to repair.

Looking down a steep, eroding bluff towards Little Cliff Pond.

Nickerson State Park has beautiful ponds with steep banks.  But there are several ponds there with serious erosion on their bluffs.  One of the ponds became so unbalanced from nutrients in 1998 that two dogs died within ten minutes of entering the water.  The cause--a toxic algae bloom, resulting from too many nutrients washing into the water.

A fragile park

Vegetation in Hawksnest State is fragile, because the soil is thin, underlain by loose sand.  There are steep bluffs overlooking the water to the west and north of the pond.

Shore vegetation is especially fragile, because it has become adapted to a sheltered environment.  Along the edge of small ponds, there's little wave action or movement of winter ice.  Interior ponds are different from the ocean shore, where storms and currents normally cause much erosion.  Coastal plants and animals have become adapted to change.

The fragility of Cape soils was revealed in historic times.  In portions of the Provincetown and Eastham, the sandy soil became destabilized from overgrazing or farming--resulting in barren plains or even roving dunes.*

In desert, alpine, or arctic landscapes, erosion can take a very long time to heal.

But on Cape Cod, erosion can heal relatively quickly after disturbance stops, because of the gentle slopes, mild climate, and humid air.  At many locations in and around Hawksnest, you can see the scars of old roads or borrow pits, now healed over.

While Cape landscapes can mend when disturbance stops, ponds can't heal so easily. Once excess nutrients reach the pond, most of the nutrients stay forever.

Shorelines are especially vulnerable, because they attract people to a narrow strip.  And shorelines are also more prone to erosion because of steep slopes, wet soil, or wave action.

When shorelines erode, there's noting to prevent the soil from going directly into the lake or stream, where it contributes to overfertilization.

Most shores of lakes and streams in the US are severely degraded--taking a toll on water quality.  But at Hawksnest Pond, the shore and its ring of protective vegetation is remarkably intact.  Not a drop of water gets into the pond unless it seeps through the sand, or through the filtering ring of plants.

The intact shoreline is one of the reasons Hawksnest has the best water quality of any pond in Harwich.

Hawksnest is remarkably well-reserved because it was private property until 1970, then was protected by terrible roads.  If we can keep the shorline intact, it could be an example for the whole country.  Almost everywhere else, people have forgotten what a natural shoreline can be.

Boardwalks for Hawksnest

Recognizing the damage that can occur, many parks have built boardwalks over paths where the traffic is too heavy, or the vegetation is too fragile.

Boardwalks like these are needed at Hawksnest.  When water levels are high, there's no beach, so swimmers trample shoreline plants.

If  we built a few boardwalks down to the beach, we'd have easier access, a more beautiful shoreline, and cleaner water for all time.

It's time to recognize what a gem we have in Hawksnest, and do something to protect it from careless abuse.

Cape Cod National Seashore, at Provincetown.

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Slide show: Boardwalks around the world
Slide show: Loving Walden Pond to death
* Barren landscapes described by Thoreau in Cape Cod.

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