Return of the wet

Exploring the responses of some plant and animal communities to two years of drought-ending rainPublished 13/12/11 | by Karl Just

It was the longest drought in recorded history, and I think many of us were beginning to wonder if it would ever end. Was this the new climate? Was global climate change already well under way? The bush was just getting drier, plant populations were dwindling, and most wetlands had been reduced to tired dust-bowls, covered in weeds and colonizing terrestrial species.

But in the last two years the drought has been well and truly broken with some equally extreme wetting events that included record flooding, weird hailstorms and some relatively cold summers. La Nina, the sister of El Nino, was finally back on the scene. Whereas in the years 2006-2009 the yearly rainfall failed to clock over 465 mm, in 2010 we received 780.2 mm and in 2011 834.6 mm (recorded at the Melbourne Regional Office). I also just heard on the radio that the year 2011 was one of the three wettest in Australia’s history.

In Victoria the return of decent rains has led to some exciting responses from many different plant and animal communities. It has been fascinating to observe the extreme resilience and adaptations of many of our flora and fauna to long-term drought conditions, and to see just how quickly some species can bounce back to life. Birds have been busy nesting, plants re-shooting from chewed stems or regenerating from rootstock and seed-banks, insects breeding en-masse. This article will provide some observations taken over the last two years of some special areas or individual species that have responded particularly positively, as well as a few downsides.

Swamp Pipewort Rediscovery

During 2008-2009, I went on several field trips with a friend from DSE to search for the Swamp Pipewort, Eriocaulon australasicum, in shallow ephemeral wetlands around Edenhope and the southern Grampians. This species is believed to be endemic to Victoria and had not been observed for over twenty years, leading to fears that it may have become extinct during successive droughts. Although we searched for days, we failed to locate any plants. It appeared that although the wetlands had some water in them, they were not remaining wet long enough over the summer period, which is when Swamp Pipewort usually grows and flowers. However following heavy rains in summer 2010/2011, Swamp Pipewort was rediscovered at two locations, including at one of the small wetlands we had searched several times during the drought. Many plants were found within populations, and it appears that the species is fairly well adapted to surviving long drought conditions, emerging from dormant seed-banks when the time is right. Seed has now been collected to allow ex-situ propagation and management.

Red Gum Swamps

Wetlands of the northern volcanic plains

The Moolort Plains occur on the northern portion of the Victorian Volcanic Plain, between Newstead and Maryborough. Sadly most of the original grasslands and grassy woodlands of this area have long been cleared for agriculture, but the plains still support a series of beautiful River Red Gum swamps. Like the majority of wetlands in Victoria, during the drought the swamps remained dry for many years, leading to the decline in tree health and the number of visiting water birds. But since decent rains returned in 2010 the wetlands have been full for over a year, and have only recently begun to dry out. It has been very heartening to see these majestic wetlands full of water again, and to observe the return of plant and animal life. Some of the swamps are crammed with water birds, including large flocks of waterfowl, Blacktailed Native Hens, Spotted Crakes and even sightings of the very rare Painted Snipe (Damien Cook pers. comm.)

This is a common story that is shared by many of Victoria’s wetlands, which were bone dry for many years during the drought. Now almost all have been filled, from shallow grassy wetlands to huge lakes and floodplain swamps. The wetland birds survived the drought by hanging out in scattered refuge sites (areas supporting more permanent water), and are now flocking back and breeding, while plants are recruiting from seed banks and dormant rootstock.

Terrick Terrick Grasslands

Northern plains grasslands

In early spring 2009 I went on a trip with a few other botanists to visit some new grasslands reserves that had been proclaimed on the northern plains in the vicinity of Kerang. We also visited some of the best grasslands at Terrick Terrick National Park north of Mitiamo. Most were looking amazing, with huge displays of wildflowers. There was a profusion of colourful daisies, including Small White Sun-ray, Rhodanthe corymbiflora, Rough Burr-daisy, Calotis scabiosifolia and Beauty Buttons, Leptorhynchus tetrachaetus. Local ecologists explained how the many years of drought had reduced the cover of grasses and created large bare areas, which had now been colonized by masses of annual wildflowers in response to the good rains. It was predicted that with a few more good years the grasses would again regain much of their former cover, and so the show of wildflowers would not be quite as amazing as during this first year of rain.

Gunbower National Park

River Red Gum floodplains

The floodplains of the Murray River have been suffering for many years, starved of water to feed the wants of agriculture. The long drought exacerbated this process and led to the death of many River Red Gum trees, decline in waterbird breeding events and loss of cover and diversity of wetland plants. But following extensive heavy rains throughout the catchment in 2010, the Murray finally swelled and spilled onto the floodplains of Gunbower and Barmah. The response has been pretty inspiring. During a walk through the Gunbower Forest in early January 2011, I waded through half a kilometer of water up to my knees. The water was full of aquatic plants that had emerged from seed banks and dormant tubers, and many dragon flies could be seen flying around and mating. I had walked through this area the year before, when it had been covered in drought tolerant chenopods and weeds. It was one of the most drastic transformations of a plant community I have ever seen.

During some surveys at Gunbower a few months later, the water had greatly receded. Warrego Summer-grass, Paspalidium jubiflorum, a dominant species of some areas of Gunbower, had grown to over a meter tall, creating dense green grasslands. It reminded me of a sub-tropical savannah. These areas had previously been almost bare of plants, but the grass had managed to re-shoot vigorously from shriveled stems. Many of the River Red Gums showed signs of recovery, producing fresh green growth, while diverse herbfields occupied many of the floodways.

But contrary to what many appear to think, the latest flood was far from sufficient to quench the thirst of the Murray floodplains. These ecosystems are adapted to small floods every 3-5 years and bigger floods about every 10 years, but are currently only experiencing very occasional small to large floods. Works are currently underway in the newly created Murray River National Parks to allow regular allocation of environmental water to these ecosystems, however the current allocation stipulated in the Murray Darling Basin Action Plan is far from sufficient to save these forests.

If you would like to see more water go to the floodplains now is the time to write a submission at http://www.mdba.

Mickleham Woodlands

River Red Gum grassy plains

In 2007 I was asked to conduct a flora survey of the northern area of the Mickleham Woodlands in Donnybrook. At the time the land was still in private ownership and was being grazed heavily by cows. The grazing in combination with many years of drought had a real impact to the woodland understory, and it was hard to find many plant species. Although it was apparent that there were gilgai wetlands and shallow grassy meadows present, these were very dry and pugged. But in late 2011 I was told that the stock had been removed and that the wetlands had revived. I visited the site and was amazed at what I saw. The gilgais were full of species that I had not even observed during my former assessment, including several species of Swamp Wallabygrass Amphibromus and swags of Spike-sedge, Eleocharis acuta and E. pusilla. Several beautiful shallow meadows had appeared where I found floating plants such as Myriophyllum and Potamogeton. Best of all, there were even some rare species including Eliocharis macbarronii and several plants of Utricularia beaugleholei (the later species very restricted on the VVP in Melbourne where only known from a couple of sites). It will be interesting to see how the woodland and wetland areas continue to respond, hopefully assisted with some management to combat the weeds.

Castlemaine Diggings National Heritage Park

Box-Ironbark forests

Since the breaking of the drought there has been a drastic transformation in many areas of box ironbark forest in central Victoria. These vegetation communities occur in areas that naturally receive low rainfall, but during the drought they were particularly parched for water. This process was exacerbated by grazing by hungry wallabies and kangaroos, reducing some plant species to nothing but heavily chewed stems. But in the last two years there has been some terrific growth and flowering, particularly of shrub species. This was very apparent in parts of the Castlemaine Diggings National Heritage Park this year, where stunning wildflower displays could be seen. Some areas near my home at Fryerstown were a dazzling array of colour, with the white of the Fairy Wax-flower, Philotheca verrucosa, purple of the Black-eyed Susan, Tetratheca ciliata, and the yellow and reds of a variety of peas and wattles. This was all brilliantly contrasted against the darker brown and blacks of the Red Ironbark and Red Stringybark. The recovery of the Fairy Wax-flower was particularly surprising, as only the year before it seemed hard to find because of the effects of browsing pressure. But in 2011 it seemed to be everywhere, with large plants that had re-shooted vigorously since the rains. Unfortunately the orchid season was not so good in 2011, with some dry months in spring impacting this suite of species.

Some downsides

Unfortunately it’s not all good news. The massive amount of growth of many indigenous plants has been equally matched by the growth of the exotics. This is particularly apparent with annual grasses and herbs, which have recruited in large numbers in response to the rain. This is a common strategy of many annual species, which often have long-lived seed banks that lie waiting for a good year to recruit en-masse. At many sites where I have helped remove weeds over the last few years we thought we had the weeds beat, but now we are facing some difficult challenges.

Across the volcanic plains you may have noted the massive growth of Kangaroo Grass, Themeda triandra, over the last two years. During the height of the drought this species appeared to hardly grow at all, making some grasslands look pretty flat and sparse. But since the rains most intact volcanic grasslands are now choked with Themeda growth, in many cases up to a meter tall, leading to concerns it may outcompete inter-tussock forb species. At one site at Deer Park, a critically endangered orchid is now hard to find amongst the grass, where two years ago I could easily find over 100 plants. The Themeda grasslands desperately require burning programs before the herbs are out-competed, but sadly little is happening. This is partly due to the difficulty of planning burns during such wet autumn and spring weather, but I think mostly because of a bad priority system. It is sadly ironic that the Department of Sustainability and Environment is currently attempting to burn huge areas of forest across the State that don’t even need a burn (only to achieve unrealistic targets set by the Royal Commission after 2009), but are planning few burns in the ecosystems that really need it.

Lastly, the flash-floods have caused damage to many of our rivers and creeks. The banks or many of our streams have already been weakened by processes such as rabbit and stock grazing and clearance of riparian vegetation, and so they have become especially prone to erosion during flash-flooding. I have seen many significant aquatic and streamside herbfields scoured during the rains, including along the Watsons Creek (Christmas Hills), Hughes Creek (Seymour) and Yarra River (Eltham). This has removed some rare and special plants, and it is still unclear if they will return.

Alright, that’s enough bad news. Overall I think there has been much more to celebrate with the return of the wet weather, with a long-needed revival of many natural areas (not to mention the benefits for farmers and our food and water supplies). So what have other people observed over the last two years? We would love to hear your stories in the IFFA forums or in future issue of Indigenotes.