The most important things aren't always the things you notice.

For many of us, southern New Jersey's coastal wetlands are just a backdrop. Something that stretches outside our car windows as we drive on the Garden State Parkway or cross a causeway to get to the beach.

But, as Press staff writer Sarah Watson noted in a recent story, those low, green marshes are teeming with life and activity. Salt marshes are considered the most productive ecosystems on the planet. And in various ways, the wetlands make our coastal lifestyle possible.

In the marshes, crabs, clams, shrimp, fish and turtles live by the movement of the tides and provide food for nesting and migrating birds.

The brackish water, grasses and mud form a vast nursery. In fact, 75 percent of our commercial fish and shellfish depend on wetlands for breeding. Our fishing industry - and recreational fishing - are dependent on wetlands.

In addition to being a home for a vast amount of wildlife, the marshes protect uplands from flooding, acting as a sponge to absorb and store vast amounts of water.

And, as they grow, the grasses and plants of the wetlands absorb pollutants and heavy metals, filtering the waters of the back bays. Experts say they capture more carbon than any other natural habitat in New Jersey.

While it can be hard to see, it all adds up. A 2007 Department of Environmental Protection study put the economic value of the state's saltwater wetlands at $1.2 billion a year.

That's why the wetlands are worth preserving. And why, in the 1970s, New Jersey adopted laws to protect wetlands and limit the amount of development that can occur nearby.

People didn't always recognize the value of wetlands. When shore towns were first developed, wetlands were routinely drained or filled for roadways, farmland and to try to control the bane of coastal living - the mosquito.

Early residents used the wetlands commercially, harvesting grasses for packing material and putting livestock on marsh islands to graze. (A reminder of that use is preserved in the name of Cowpens Island behind Ocean City.)

Later, haphazard shore development destroyed more wetlands. It is estimated that New Jersey now has about half the freshwater and saltwater wetlands it once had.

And as productive as they are, our remaining wetlands are also fragile. They are threatened by rising sea levels and runoff of pesticides, fertilizers and sediment from development.

Once you lose wetlands, it is hard to get them back. Mitigation projects in the state have had mixed success.

That's why New Jersey has to take seriously wetland violations - such as dumping, filling or construction without permits - and why we should all support efforts to preserve this valuable ecosystem.