Natural Regeneration Works with a Little Help from Friends

A 15-year old experiment on the Ohio State University’s campus showed that wetlands left to regenerate naturally produced just as much ecological services as wetlands deliberately planted by humans. Researchers at the University have been assessing the relative performance of 2 experimental wetland marshes on the campus. One wetland was deliberately planted in 1994 with wetland vegetation. Another marsh was that was left on its own to become colonized with plant and animal life through natural processed. After year 15, the two wetlands featured almost the same number of plant species. Also their rates of retaining nitrates and phosphorus were almost identical and both wetlands were effective carbon sinks retaining carbon in their soil and biological communities.

In some ways the naturally produced wetland was better. It contained more plant biomass. However it emitted more of the methane (a greenhouse gas), because it contained higher stored biomass of decaying organic material from the higher biomass production.

More methane was produced from the bacteria supported decaying process causing the natural wetlands to release the gas into the atmosphere.

Within about 5 years, both of the marshes contained about 100 distinct species each, and this plant diversity continued to increase throughout the study period to the end of 2008.The researchers were surprised that the diversity and variety of types of plant species rose so quickly. After only 5 years in 1998, the naturally developing marsh featured 87 species and the planted wetland has 96 species. Those numbers increased to 97 and 101 species, respectively, by 2008.

The researchers have forecast that the two wetlands will continue to increase their stores of carbon in their soil and ecosystems at a steady pace for many years to come, up to about 50 years when the ecosystems will reach final maturity.

This study showed that wetlands can be cost-effective and efficient tools to tackle carbon emission problems while adding valuable ecosystem services, such as water quality improvement and flood control as well as increasing the flora and faunal diversity of the local area.

In Australia two stories show how effective regeneration can be in establishing local wetlands.

On the north Coast of NSW fisheries researchers found healthy populations of fish in what appeared to be a natural patch of rainforest at the head of gully. However after speaking with the locals it became clear that the area showcased a natural regeneration process. How can a rainforest be regenerated with all its high species diversity and canopy structure. The elements of the story were as follows:

• Thirty years ago the area has been completely cleared and planted as a banana plantation. The area was steep and a flying-fox system of cables was used for transporting the harvest.
• Due to disease and other problems the property was sold to a group of hippies.
• They tried to manage it but the area was taken over by Lantana and blackberries.
• They cleared a few small patched and planted an orchard, however most of the property was not managed, nor the weeds controlled.
• What happened was that several pioneer rainforest species called Sally Wattles (Mimosa floribunda) became established - probably from seeds dropped by birds from the local rainforest remnants. These small trees grew above the Lantana and produced shade that cause the demise of the Lantana under their canopies. This allowed more species to become established.
• This process continued and after 20 years the entire area was covered in regenerated rainforest with a species diversity similar to that of the surrounding forest remnants.

Further north an innovative approach was used to overcome a problem with a tropical stream in Tropical North Queensland.

A cattle farmer was having problems because his cattle were becoming trapped in a water soaked bog. The cattle had tramped the banks and turned a lovely rainforest stream into a wide muddy bog that had spread out and consumed valuable farmland. The cattle had creating a huge mess and problem for the farmer and the cattle could not drink safely from the stream. The farmer wanted a safe watering point for his animals and the local environment group wanted to restore rainforest corridors along the stream and to get the stream back into its original watercourse.

The actions taken were:

• The area was fenced off and a watering point armoured with rocks constructed for the cattle.
• Some minor works were done to provide a defined precursor for the restored watercourse to provide an initial path for the stream.
• The area was sprayed with herbicide to kill the grass and weeds.
• About 10 tree species were planted. The seedlings were mature - about 2 years old and about 1-2m high. They were planted very close together - about 1.5 to 2m apart. The aim of this planting was to close the canopy within 12 months to control weeds and grass. The species used were carefully selected and were - hardy pioneer species, bird attracting and fast growing.
• Controversially, two of the species chosen were not rainforest species and were no endemic to the area. Why? Because the species were known to grow quickly to stabilise the banks and could quickly produce the shade needed to control weeds and grass.
• The planting strategy had two main aims: Close the canopy to control weeds and attract birds to the area from the local rainforest remnants nearby. The birds would bring seeds to the area in their dropping which could develop in the shaded areas. The shade would stop the local weeds and grass that needed full-sun to grow. Rainforest species on the other hand, are well adapted to grow in shade.
• The area chosen for the pilot was not in the headwaters but on the main road close to the town so that the local farmers would see the results.

The outcome? The strategy worked very well. Within 3 years a beautiful patch of rainforest had been established along the stream which had re-incised its channel and had reverted to a confined flowing stream with clear water.The number of species had grown from 10 to 27 and the diversity was increasing rapidly. The area had become a local show-case of what could be achieved and many other farmers were keen to adopted similar projects on their properties. The conservation group was happy that a small patch of rainforest has been regenerated and they were well on their way to re-establishing rainforest corridors along the stream. The weeds were controlled an there were the problems with bank erosion and water quality had been partially addressed. The farmer was happy and the cattle could drink from the stream without getting bogged and destroying the banks.

Conclusion: Natural Regeneration Works with a Little Help from Friends