Wise Use of Wetlands

Wetlands conservation is increasingly recognised as an important part of biodiversity and threatened species conservation. For this reason the Department of Environment, Water, Heritage and the Art's National Wetlands Program promotes the Wise Use of wetlands to help prevent wetlands from becoming degraded and lost. In Tasmania it is estimated that 50-60% of the original wetlands have been lost, primarily by being converted to other land uses. Their ecological importance in maintaining biodiversity is as significant as a tropical rainforest yet they remain poorly understood, largely because their public profile has, until recently, been minimal.

Wise Use refers to the sustainable use of wetlands for human activities whilst at the same time preserving the integral naturalness and biological balance of the wetland. Wise Use provides a win-win situation for everyone, nature and man alike. It allows for humans to enjoy the wetland and pursue their activities without damaging the wetland system upon which they and other animals and plants depend. Understanding that ecosystems depend on the sum of their parts and that by removing or significantly altering one part, then the whole is detrimentally affected through a domino effect, is paramount in implementing Wise Use strategies.

Seasonal Changes

A major feature of a wetland is that it is wet! However, a wetland does not have to be wet all the time. The most biologically productive wetlands are those that dry out periodically, have a range of water depths and have plant communities which change with the year's seasons. In Australia Lake Eyre is the best known ephemeral wetland, only becoming inundated when unusually wet seasons bring river floods from northern Australia.

In Tasmania wet and dry periods generally follow the year's seasonal changes, so it is important that human activities such as dam building and irrigation do not change the natural flow regime. Many wetlands in Tasmania will dry out in the summer months and become inundated again with the winter rains. These wetlands contain numerous types of floating, submerged and emergent plants which are dependent on the wet-dry periods. If a dam is built on a feeder stream then this pattern may be changed and the wetland will not receive sufficient winter flows to ensure the survival of those plants and animals dependent on the inundation period. Similarly, if irrigation is undertaken from a wetland during summer then the drying-out phase will be accelerated and the plants and animals will be affected.

Drainage

Drainage systems can also significantly alter a wetland's water regime and increase the risk of sediment and chemical input to the wetland. Drainage systems implemented to help reduce soil salinity may cause salts to be transported to downstream wetlands, thereby increasing their conductivity levels and altering their 'fresh water' status. It is therefore important when undertaking improved drainage works to consider the effects on wetlands. Not only from a nutrient and sediment perspective but also how the added water input will affect the water balance and quality within the wetland.

Wetlands on Private Land

For wetlands on private land in Tasmania, a best management practice would be to fence the wetland and prevent stock from walking into the water and grazing on riparian vegetation. It is also recommended that a buffer zone be fenced around the wetland. This buffer zone can be used for light stock grazing at minimum impact times, for example in summer and autumn, when drier conditions reduce the erosion effect of stock hooves and pugging. These buffer zones can provide a landholder with good feed during the harder months when there is less in the paddocks. However, it is preferable that within these buffer zones stock cannot access the wetland itself or the riparian vegetation.

Buffer zones are also important as they capture a major part of nutrient and sediment run-off before it enters the wetland. Buffer zones need to be well vegetated, preferably with native grasses, sedges and rushes and where applicable a good woody upper canopy of trees and shrubs. The species component of a buffer zone depends on where the wetland is, ie. coastal, forest, open woodland or heathland. Weeds can present problems in the riparian and water zones, out-competing native vegetation and thereby reducing the food availability for native animals. It is therefore important to try to keep these areas free from weeds.

The buffer zone should also be kept free of fertiliser and pesticide applications and if aerial methods are used then care needs to be taken not to allow over-spray or drift into the wetland. Many wetland animals and plants are highly sensitive to chemicals. Frogs are now well recognised as being key indicators of biological health - the "canaries" of ecosystems. Many badly degraded wetlands have poor diversity and low numbers of frogs. When a wetland is rehabilitated the return of frogs is one good way to determine how effectively the rehabilitation program is working.

Wetlands on farms provide an excellent emergency water source for stock in harsh drought conditions. By erecting a watering trough (ideally outside the buffer zone) stock can have access to the water without disturbing and damaging the wetland itself. Wetlands also act as natural fire barriers, even when they are dry the succulent plants and damp sub-surface helps to break a fire's course.

Recreational Activities

Many wetlands have numerous human activities taking place on them such as boating, fishing and water skiing. However if a wetland has not had such activities then it is preferable that it remain undisturbed. Stocking wetlands with introduced fish species for recreational fishing purposes, for example, can have significant detrimental effects. Exotic fish are generally more aggressive and competitive than native fish species, they are also a lot larger. In many lakes where trout have been introduced the native fish have declined or become extinct. Exotic fish will also eat frogs and / or frog spawn and effectively reduce the number and diversity of frogs within the wetland. It is therefore preferable to limit exotic fish species to very specific lakes and dams.

Exploring a wetland by boat is always inviting but the choice of boat is important in order to minimise pollutants entering the water. Most outboard and inboard motors discharge fuel and oil into the water and they are generally noisy. In order to minimise the impact of these pollutants it is important to ensure the engine is maintained to a high level of efficiency, uses biodegradable oil and discharges as little as possible. The best way to explore a wetland is by paddling or rowing as neither of these activities disturb the animals and it is possible to observe and get close to many animals, for example platypus and water birds.

Photo-points

Wetlands are there to be enjoyed by everyone and need to be protected so that future generations can equally enjoy them. Setting-up photo-points is a great way to observe a wetland over time. Photo-points provide an opportunity to observe seasonal changes but also to observe annual changes. Where a wetland has become degraded but is undergoing best management practices to regenerate it, photo-points provide an excellent tool to monitor the positive effect such practices are having.

By implementing the Wise Use principle the best possible outcomes are achieved for present and future human, animal, plant and microbial generations.

Written by Janice Miller, World Wildlife Fund

Contact

Natural Values Conservation Branch
200 Collins Street
HOBART TAS 7000
Phone: 03 6165 4401
Email: NaturalValuesConservation.Enquiries@dpipwe.tas.gov.au

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