The Permacultivator - Journal of Cool Climate Permaculture
The current debate about the siting of a new Council tip above the protected wetland of Hanging Rock Swamp raises the issue of what can be done to save our remaining wetlands from degradation.
Wetlands are often referred to as nature's kidneys because of their valuable role in the natural ecosytem. They filter and purify water, trapping potential pollutants and removing excess nutrients. They re-charge groundwater in underground aquifers and act as vast natural sponges, soaking up surface water and releasing it slowly in times of drought. Freshwater peatlands also act as carbon sinks conserving vast quantities of carbon that if dried or burned would contribute to the Greenhouse Effect.
Governments are gradually recognising the valuable contribution wetlands make to the environment and are even experimenting with creating artificial wetlands (such as the Water Board Arncliffe project) to help cope with the problems of city stormwater runoff, pollution etc.
Rivers run with battery acid
But creating artifical wetlands is no excuse for destroying natural systems. The massive Belmore swamp on the Macleay River in northern NSW once covered 1,300 hectares and was flooded for six months of the year. But the Government set up massive drainage schemes to reclaim the land and now a remnant of the swamp fills for barely six weeks of the year. The effect of this has been monumental. A valuable breeding ground for fish (a multi-million dollar industry) has been lost forever and the acid run-off from the drained swamp is unbelievable. Swamps are high in iron compounds, sulphates and aluminium silicate. When surface water is removed these compounds are exposed to oxygen and chemical reactions occur. Heavy rain or flooding has been known to flush run-off down rivers with pH levels of 1.9 - almost equivalent to battery acid!
Such a scenario may be in store for the Paddy's River Wetlands if the proposed Council and Collex landfills are constructed above Hanging Rock Swamp.
Acid waters ... lower water table
The Paddy's River Wetlands take in Hanging Rock Swamp, Stingray Swamp, Long Swamp, Mundego Swamp and Uringalla Creek. These areas all flow into Paddy's River which in turn flows into the Wollondilly River and Warragamba Dam. This massive wetland system is believed to be fed by a vast underground aquifer. To consider constructing a Council tip in such an environmentally sensitive area is irresponsible but to contemplate a massive mega-tip containing 13 million tonnes of rubbish perched above the wetland is unthinkable! Containment dams on both sites would divert considerable surface water run-off away from the swamp, leading to increased acidity in Hanging Rock Creek as well as diminishing the swamp's capacity to recharge underground aquifers. Plans to clear-fell the nearby Penrose State Forest will also increase acidity in the waters as well as lowering the water table.
The battle to save Hanging Rock Swamp will probably be waged by politicians over the next State election. The need to preserve wetlands, however, can be tackled by any backyard permacultivator with a lot of enthusiasm and a little local knowledge.
Natural wetlands for Zone 5
In a permaculture design Zone 5 is generally considered to be the unmanaged natural environment, an area of wilderness preserved as a wildlife corridor or for recreation. There are some good reasons for including a natural wetland within this zone, not least of which is the contribution one can make to restoring nature's balance.
You may be starting with a bog, a soak, a dam, a creek, reclaimed marsh or even an open paddock. As long as water can remain above ground over a period of time then you have the makings of a wetland. If you are starting from scratch then you will need some mechanical assistance to create a reservoir. A variety of dam construction designs are illustrated in the booklet Farm Dams for Wildlife and Stock available from National Parks & Wildlife. These designs could easily be modified to fit into the natural plan inherent in Zone 5.
Bear in mind that creating wetlands is quite a different water management use to swaling. Swales are designed to assist water to be absorbed. Wetlands are designed to collect water and maximise the terrestrial/aquatic potential of the edge effect. Wetlands can also be created as food-producing bog gardens and this aspect will be covered in a subsequent issue of the Permacultivator. But before we imitate nature we must first understand how the natural ecosystem has evolved and learn the management skills needed to re-create this intricate and fragile environment.
20 acres of swamps drained
A case history might best serve to illustrate the problems/solutions involved in farm wetland management. In March 1994 a field day on Wetlands on Farms was held at Penrose. The property Booroola that hosted the field day once featured 20 acres of swamps draining into Paddy's River. In the past this area had been drained (the drainage channels still dissect the area) and over 20,000 tonnes of peat-like top-soil had been removed. Excavations had extended to a depth of one metre. What was left was a vast, treeless paddock with acid soil registering a Ph of 4.5
The excavation of so much of the swamp had had a dramatic impact on water supply. Ground water had dropped to 20 feet below soil level and was not recharging at previous rates. The loss of swamp vegetation, at the bottom of a slope, also meant that soil and sediments washed down by heavy rain were no longer being held in the basin.
Use species endemic to your area
Van Klapake, a botanist engaged in bush regeneration, suggested some useful strategies for establishing or relaiming such a wetland area. The most important point is to only use species endemic to your area. This helps to retain the integrity of your environment and reduces the risk of introducing water weeds such as alligator fern or salvinia. It is also critical that a diversity of plants be established, to avoid a monoculture developing.
In the case of Boorola a remnant of the orginal swamp clung to the perimeter of the site. This vegetation could be used as a nursery with seed being collected or clumps divided and replanted in the degraded area. A word of warning at this stage: don't gather wetland plants from the bush - buy them from commercial nurseries or ask farmers to let you gather seeds or divide clumps on their properties. Waripendi Nursery at Colo Vale are building up a selection of wetland plants suitable for farm planting. Wirrimbirra at Bargo also offer a selection of wetland plants. In the case of wetland plants it may be necessary for consumers to create a demand so that a legitimate supply will eventuate.
One of the most characteristic plants of wetlands are the sedges. Sedges are useful in stabilising soil, preventing erosion and inhibiting weed regeneration. Lepidosperma (Sword sedge), Baumea juncea (Swamp sedge) and Chorizandra sphaerocephala are useful species endemic to the Penrose area. Lomandra (Mat Rush) is another useful species; the tufted variety of Mat Rush has become very popular in landscape planting as it is a good groundcover and protects banks from erosion. Gahnia sieberana (Sword grass) is a distinctive sedge often found in dense clumps along waterways; resist the urge to plant it in regular lines as this effect is most unnatural.
Other swamp natives that establish quickly are Hypericum japonicum , Goodenia , Lepyrodia and Coral Fern. Ferns can be very useful in stabilising creek banks and beds. Those in a creek may die during heavy water flow but those remaining on the banks will compensate for any losses. Sword grass, Mat rush and ferns are readily grown from seed or by separating clumps at the base. Gahnia seed needs time or damage to germinate, so the seed will need to be scraped against sandpaper before planting.
Encourage botanical diversity
Plants such as Leptospermum attentuatum (Tea tree) germinate readily from seed and quickly cover an area but they must be interspersed with sedges and other plants to prevent a monoculture developing. Planting a variety of trees and shrubs along waterways adds considerably to the botanical diversity of an area.
One of the problems facing farmers with land that has been cleared and improved could be a proliferation of competititve weeds and grasses. Sedges such as Baumea juncea are especially good for quick ground cover but grasses such as couch or kikiwui can provide some pretty stiff competition. When transplanting plants it's a good idea to pot them first so that weed seeds that may have been in the soil will have time to germinate before the plant itself is planted out. Pots should be immersed in water or continually soaked.
Warning on weed killers
Some people recommend the use of a commercial preparation such as Round Up to kill off grass before replanting. However it is worth noting that some commercial formulas have a longer half-life than previously considered safe and even in dilutions of one in a hundred are still capable of rendering crustaceans infertile. So if you plan to stock your wetland pond with yabbies, bear this in mind.
Strictly for the birds
Apart from yabbies one of the other bonuses of a wetland environment is the variety of bird life that will be attracted to the area. Small parrots, honeyeaters, finches and wrens are likely to appear, as well as ibises and water fowl.
Shallow areas are needed , such as marshy ground feeding into a dam, for small birds such as pasturines who drink in reed areas. An island for bird shelter is also advisable as birds like the Japanese snipe need protection from predators such as foxes during the day.
Sedges such as Eleocharis sphacelata (Spike Rush) are excellent for nesting and protecting small native birds. Duck weed provides food for birds and as they frequent a wetland area birds will bring in seed on their feet, thereby assisting a more complex food chain to evolve. Eleocharis is, incidentally, very useful for polishing water - removing nutrients etc. and is often used in a monoculture situation in artificial wetlands for this very reason.
Encourage a diversity of habitat
If your potential wetland is already dominated by a particular species, such as Tea tree, it might be necessary to physically remove some by hand. Next stage would be planting a selection of sedges to act as a ground cover which would also help to make the system self-containing.
In the water itself, avoid the use of bulrushes as they tend to dominate the shallow end of the pond. Baumea is just as good without being too vigorous. Don't forget to provide sufficient shallow areas to encourage a diversity of habitat and plant life. When the ecosystem is in balance insects, snakes, frogs etc. will all be catered for. Aquatic vegetation is necessary for producing insects for birds and so on in the food chain.
Take the opportunity to look at a natural wetland to get some idea of the species endemic to your area and the natural complexity of plantings. At Stingray Swamp Flora Reserve at Penrose an incredible diversity of plants is evident. At the edges of the swamp lies a woodland fringed with eucalypts such as Paddy's RIver Box, Peppermint Gum etc. Further towards the swamp one finds hakea, banksia, gahnia, epacris, button grass, baumea, coral fern, Chorizandra , liverworts and spaghnam moss. Spike grass will grow in deeper water than other sedges. Eucalyptus aquatica (Mountain Swamp Gum) is a resident of this wetland system and also likes to have its feet in water making it a very useful plant for a wetland. It rarely grows above 3 metres in height and is endemic to the Penrose area.
The Department of Water Resources are keen for farmers to conserve wetland environments. The Department has produced a series of free publications dealing with buffer zones, blue-green algae, farm dams etc. that would be relevant to anyone contemplating creating a wetland.
Putting back the swamps
Perhaps one of the most inspiring accounts of wetland reconstruction is told in the publication Bushland on Farms. In 1959 John Fenton inherited the property Lanark in Victoria from his father. Since then he has planted over 35,000 trees and has operated on conservation lines, with no insecticides or sprays and very little fertiliser application over the last 25 years. The property stocks fewer sheep to the hectare but this actually increases the productivity of the farm. Fewer sheep mean less feed is required, no hay is needed to be cut and less labour and machinery costs are involved. Smaller flocks minimise soil compaction and prevent soil erosion. Less competition for grass and the provision of trees to reduce stress levels in sheep means more energy is utilised in wool and meat production. In addition, no superphosphate cuts out stock troubles, such as ryegrass staggers. John practices sustainable conservation techniques and is the founding father of Rural Trees Australia.
One of John's major triumphs has been the conversion of fifty-six acres of grazing land into lakes and water meadows. These areas had previously been drained and most of the native timber cleared. As part of a total farm management plan these areas were flooded and a wetland re-created, but one with very real practical values. For instance, a horsehoe swamp was built around the house to act as a fire break. The Victorian Fire Authorities use Lanark to demonstrate the use of wetlands as a fire protection strategy.
The water areas on the property now provide reliable pasture and water in times of drought. They are visually attractive and form an excellent fire break. They also encourage over 140 different birds and water fowl that effectively reduce insect levels on crops and pasture and minimise the use of chemicals for pest control.
Birds reduce insect levels
The real measure of John's success at Lanark is in the return of ibises. One area of drained swampland on the property had been bare-grazed for 70 years. This area was reconstituted, revegetated and completely fenced for 20 years. In 1983 three pairs of white ibises nested in the reed beds. By 1987 over 250 pairs were nesting in the ibis rookery. A straw-necked ibis or a white ibis will eat around 200 grams of insects, such as grasshoppers and crickets, each day, so you can see the value in attracting such birds to farms.
A wide selection of birds can effectively reduce insect levels on crops and pasture and minimise the use of chemicals for pest control on farming properties. The wetlands on Lanark as well as being visually attractive now attract 147 different birds and water fowl . Of the birds now found at Lanark 33 per cent returned with the tree planting and a further 33 per cent came back when the water was replaced.
Wetlands in farm management
Retaining, restoring and even creating wetlands should form an important part of a farm management strategy, especially in areas associated with the ever diminishing upland wetlands of the Southern Highlands. More wetlands on farms means a greater diversity in the type of natural vegetation. It also means that water entering our river systems and recharging underground aquifers has had a chance to be filtered by one of the most natural methods around.