Mike Bremers gives an overview of a field trip into Kosciuszko with paleobotanist, Professor Geoff Hope, learning about alpine wetlands and how they are impacted by feral horses.
At 10 am on Saturday 2 February 2019 about 40 people gathered at Long Plain Hut in northern Kosciuszko National Park for an excursion to view damage caused by feral horses. The excursion was organised by the Reclaim Kosci campaign and coincided with World Wetlands Day. It was appropriate that the excursion was held on this day as much of the feral horse impacts are on the fragile alpine wetlands.
We first travelled to the Murrumbidgee River near the Peppercorn Trail bridge. Here we observed a horse crossing that had caused a bank to collapse that was still actively being damaged each time a horse crosses it. Along the river were other collapsed banks which, while not as noticeable as the horse crossing, clearly were being widened over time as horses go for a drink or feed on the riverside grasses.
Our guide for the day was Emeritus Professor Geoffrey Hope of the ANU. Professor Hope is an expert in studies of impacts on landscapes. He measures vegetation change (using pollen, charcoal and phytoliths) and geomorphic consequences — erosion, silting and shifts in production. A further interest is the peatlands of South East Asia and Australia in terms of wetland process, extent, carbon sequestration values and rehabilitation after burning or clearing. He has also been a member of the Kosciuszko Wild Horse Independent Technical Reference Group.
Fens, bogs and peatlands
We walked a few hundred metres upstream to a fen. Professor Hope explained the importance of fens, bogs and peatlands to the alpine environment. These wetlands act like a giant sponge which slows down the flow of water when it rains and slowly releases the water over time. This means that in dry times the creeks and rivers continue to flow, providing and maintaining habitat and reliability for water for downstream users. By slowing the flow of water, the wetlands trap sediment and reduce the chance of high flow pulses after rain, which can lead to erosion of river banks. The alpine wetlands cover 30km2 and have an average depth of 2 metres, mainly comprising peat, which is 90% water. This amounts to a substantial reservoir of water that is slowly being released into the river system.
Professor Hope explained that fens are low-lying marshland that are frequently flooded by rivers during and after rain events. The fens slow down the water, which gradually returns to the river. The fen we were observing had signs of feral horse damage (dung and hoof prints) and it was evident that a natural channel through the fen was being used by horses. The grasses growing in the channel had been eaten and there were hoof prints.
Professor Hope explained that while there was evidence of horse damage in this particular fen, it had not reached a stage of irreversible damage. All it required was for the horses to be removed and this fen would recover without any extra rehabilitation works. This needed to be done urgently because horse numbers have increased rapidly in the last five to ten and continue to do so. However, if the horses continue to impact the fen the natural channel could become incised, leading to the water being drained, the lowering of the water table and the drying of the peat. The fen would cease to provide its beneficial functions of slowing and storing water. When peat dries it is at risk of being washed into streams or emitted as methane and carbon dioxide as it degrades. Dry peat is also susceptible to fire and would take thousands of years to build up again, but only if the conditions are suitable.
Martin Chalk, a Waterwatch volunteer, gave a short talk about how trained volunteers take monthly measurements along various waterways. This provides for a baseline of the water quality in various creeks and rivers. While the upper Murrumbidgee has only been monitored for a relatively short period there has been a small but noticeable increase in turbidity. This is the type of data that can be used to identify changes occurring in the environment. It’s an early warning signal that may allow early corrective action before a major problem occurs that will require more expensive rehabilitation.
Over lunch there was an interesting discussion with two former Kosciuszko National Park rangers covering various feral horse control methods. While in the past, when horse numbers were much lower, some control methods may have been effective in controlling populations, these methods alone are no longer effective (e.g. passive trapping) or are deemed to be inhumane (e.g. brumby running). Many trapped horses have ended up at an abattoir in South Australia. It was noted, however, that there are some uses for trapped horses. There was a very successful program for disadvantaged teenagers being involved in horse breaking. It generally was agreed that trapping could continue in the more accessible parts of the park whereas the only cost effective and humane option in the remote areas was culling.
It was also noted that horses eat grass down to ground level. So rather than there being long tussocky grass, the ground resembles a recently-mown lawn (e.g. Cowombat Flat near the source of the Murray River). This means that in winter there is no subnivean zone – the intermediate snow-free layer between the ground and the snow. This zone is important for many small animals as it provides protection from the elements and predators during winter.
After lunch we drove further north to Little Peppercorn Flat. When we stopped, Professor Hope made a beeline for a sphagnum bog he had studied over many years. It was a large one. Professor Hope explained that it was healthy – the candle heath that grows through the sphagnum has protected it from feral horse damage. The horses do not like to eat the candle heath so have no reason to venture into this area. This good news was tempered by the scene a couple of hundred metres down the slope on the other side of the road where there was clear evidence of feral horse damage to a creek as shown by pugging and horse dung along the creek. This has resulted in headward erosion of the creek bed down to a hard clay layer. This was a disturbing scene for anyone who loves the mountains. Restoration of such an area would require, after removal of horses, rehabilitation works to prevent further erosion of the creek and to allow recovery of the banks.
Close to the creek we found the remains of an alpine crayfish. This was later identified by an aquatic ecologist as either “Rieks Crayfish” (Euastacus rieki) or “Alpine Spiny Crayfish” (Euastacus crassus), both of which are endangered and only found in Australian alpine areas. We wondered whether this specimen had died as a result of direct impact by a feral horse (i.e. stepped on) or due to indirect feral horse impact (i.e. loss of habitat resulting in exposure to predators). In any case it illustrated that an endangered species was trying to survive in an area that is badly degraded by feral horses that have been protected by the NSW government in a national park.
In summary it was a very interesting and informative day. The main point was that there are still some wetlands that are relatively unaffected by feral horses, but action needs to be taken urgently to reduce horse numbers to a low level to save these wetlands. We also saw that there has been some severe damage to other wetlands and that while they could be rehabilitated there is no point in doing so until horse numbers are significantly reduced.