Cinderella dams: biodiverse wetlands
In our mid 20’s Ralf and I worked for a revegetation company that specialised in revegetating wetlands both remnant and newly constructed. We established a close friendship with two beautiful passionate young men who wanted to increase and protect habitat biodiversity and did so by starting a small nursery business. They began as a team of two, harvesting seeds, sowing and planting, and grew into a team of many. Over the past ten to 15 years municipal councils all over Australia and State Governments began to realise that storm water volumes were so great that creeks were being further and further degraded and pollutants were contaminating fresh water. Over the short time that new Australians had inhabited this land, swamps and wetlands had been drained to make way for residential or agricultural developments. We had little to no understanding of the ecosystems services that wetlands/swamps provided us. These low-lying areas collected water during great down pours and allowed it to slowly filter through the soil into aquifers, creeks and rivers. They ensured a topping up of ground water, and naturally occurring bacteria and fungi in the soil broke down high nutrient levels and heavy metals. But for soil to act as a filter water must be allowed to pool for long periods of time and trickle through the soil profile before making its way to fresh water outlets. Hence today most if not all new residential developments are required to also establish adjoining wetlands.
With this experience behind us, Ralf and I were destined to create our own wetland on our 15acre property in Blampied, Vitoria. The key to creating a wetland as opposed to a dam, is to ensure that the edges of the wetland have a gently sloping gradient. A dam tries to maximise water volume by having steep sides. If you were to stand on the edge of a dam and you jumped in you would find yourself sinking deep into water. With a wetland the overall volume of water for a similar sized land area is less. If you were to jump in from the edge, your ankles would get wet. This shallow gradient (as well as water clarity and low nutrient loads: Nitrogen, Phosphorus) directly influences the diversity of plants you can establish. Just above the waters edge you can plant native flowers such as Alisma plantago–aquatica with its large heart-shaped leaves and masses of pink to white flowers, as it tolerates boggy soils. While in deeper water up to 1m in depth Baumea articulata, a tall erect tussock can be established. Baumea juncea, which tolerates inundation to 50cm can be planted between the two preceding species.
Each plant with its individual characteristics creates a home/habitat for a range of animal species or invertebrates. The greater the diversity of plants the greater the potential for attracting a broad range of micro and macrofauna to your site.
Below I have posted some images from my day on our wetland. I have planted about 25 -30 plants in the past five weeks. A very small number as the soil is really hard. The planting process includes:
- digging out competing weeds; (including Golden thistle and Gorze)
- digging a hole four times the size of the tube stock (plant size) to ensure drainage;
- mulching thickly with straw; (but not so thick that rainfall won’t get in)
- tree guarding;
- moving gear; (Mattick, hammer, tree guards, bucket, straw to the next planting hole)
- photographing work and a bit of Instagramming along the way for company.