| [Image: Protecting Coastal Wetland Forests] | | [Image: Chambers] | | [Image: photo] | | [Image: photo] | | [Image: photo] | | [Image: photo] | | [Image: photo] | | [Image: photo] |
Jim L. Chambers
Louisiana’s coastal wetland forests are of tremendous economic, ecological, cultural and recreational value. But many acres of these forests have disappeared over the past century, and many more are being degraded or lost each year. Although coastal land loss has long been recognized, the extent and critical nature of coastal wetland forest loss has largely remained unrecognized or ignored.
In 2004, a 12-member Science Working Group on Coastal Wetland Forest Conservation and Use was commissioned through the Louisiana governor’s office. Five faculty members from the School of Renewable Natural Resources were included: Richard Keim, Melinda Hughes, Craig Miller, Andy Nyman and Jim Chambers, chair. The charge for this group was to:
- Assemble the available information on the status of the forested wetlands.
- Examine the current laws, policies and regulations affecting them.
- Evaluate the regeneration situation of these forests.
- Determine the need for action.
- Make recommendations for the long-term utilization, conservation and protection of Louisiana’s coastal wetland forest ecosystem.
Louisiana has about 2 million acres of forested wetlands with more than half in the southeastern and south central parishes. Smaller areas are found along cheniers and river bottoms in the southwestern parishes. The Science Working Group recognized that both large-scale and localized alterations of processes affecting coastal wetlands have caused the complete loss of some coastal wetland forests and reduced the productivity and vigor of others. This loss and degradation threaten ecosystem functions and the many services these forests provide, including wildlife habitat, migratory bird stopover and feeding areas, storm protection, water quality enhancement, soil stabilization, aesthetics and timber production. The value of these functions and services is estimated to be nearly $8,000 per acre per year.
These forests, where present in coastal areas, may also provide important protection from storm surge during hur ricanes. Although many tree species are susceptible to high winds during storms, baldcypress and tupelo, the two most common swamp forest species, are inherently more wind firm and less subject to wind-throw (being blown down) and breakage than many other species. Swamps may, therefore, also offer wind protection to nearby low-lying communities.
The Science Working Group found that losses in ecosystem functions and services have been caused by subsidence and levee construction across large areas. Losses have also been caused by local factors such as increased depth and duration of flooding, saltwater intrusion, nutrient and sediment deprivation, herbivory, invasive species and direct loss because of conversion to marsh or open water.
At the local scale, these negative impacts have often resulted from the building of highways, railroads, stream channelization, navigation canals, oil and gas exploration canals, flood control structures, the conversion of forests to urban and agricultural land, and nonsustainable forest practices. While many of these factors have likely had some negative impact on all of Louisiana’s wetland forests, the cumulative impacts of multiple factors are greater in coastal areas.
The Science Working Group found that regeneration is a critical process of specific concern in maintaining coastal wetland forest resources. There is currently a lack of regeneration in coastal cypress-tupelo swamp forests in Louisiana. This is a direct result of the cumulative impacts identified above and their interactions with the regeneration process. Baldcypress trees have consistent seed production after age 30. But baldcypress seeds cannot germinate in standing water, and seedlings must grow tall enough during short drawdown periods for their crowns to extend above the water surface to survive multiple flood periods during the growing season. Changes in hydrological regimes (increased flooding) have reduced regeneration in many stands. Harvesting, disturbance and tree mortality – without regeneration – eliminate forest cover and promote site conversion to marsh or open water. When favorable conditions for germination and seedling growth do not immediately precede or follow a regeneration harvest, reliable stand regeneration can only occur through artificial regeneration (planting). Even planting is not possible where flooding is sufficiently persistent and deep. Without hydrological restoration (proper flood regimes), such sites cannot support sustainable forestry activities. Without restoration, these forests will eventually be replaced by marsh or open water.
(This article was published in the spring 2006 issue of Louisiana Agriculture.) |