Wetland plants: Providing indigenous food for arthropods in the heart of summer

To keep ecosystems functioning well, it is important to provide indigenous food sources for beneficial insects throughout the entire year.

As a result, insects that thrive in late summer will have enough energy to continue their daily routines. These routines often include providing helpful services to your backyard garden by assisting with pollination, composting and aphid control.

The challenge is finding indigenous plants that can cope with the arduous and dry conditions of the Australian summer. Soaring temperatures from early summer, starting in November, can put pressure on plants to survive. Thankfully, Victorian plants have evolved traits to help them cope in the month of November. Red Box (Eucalyptus polyanthemos), for example, possess leaves with a silvery shine. This colour allows the leaves to reflect more of the sun’s photon spectrum than a darker leaf colour does. In combination with a large leaf surface area, which helps maximise transpiration (the evaporation of water from plant leaves), trees such as Red Box can control their internal temperature range. Some Acacias such as Early Wattle (Acacia genistifolia) and Prickly Moses (Acacia verticillata) have waxy nodes (they don't have leaves), which help reduce water loss when opening their pores to photosynthesise.

From December onwards it becomes increasingly difficult to supply food sources in your garden for insects that provide valuable services such as pollination. Most indigenous wildflowers, shrubs, Acacias and eucalypt trees, which supply the bulk of indigenous nectar and pollen during late spring and early summer, have finished flowering by this time.  

So the burning question is: what plants flower and provide sustenance for insects from December to February? During the last two summers, I've been paying particular attention to this question. It is an important question, because this is the period when butterflies and native bees thrive. My observations have drawn me to the importance of wetlands and ephemeral water bodies in Victoria.

 An Ochre Skipper Butterfly feeding on Purple Loosestrife.  Image: Michael Smith

 An Ochre Skipper Butterfly feeding on Purple Loosestrife. Image: Michael Smith

Plants in these ecosystems often have an abundance of water. The water they suck up through their roots eventually makes its way to the leaves. The water pumps up the leaves, making them vigorous and strong. Healthy leaves mean that there is more surface area to photosynthesise, and as a result, more energy to produce flowers. So while plants in dry forests have resorted to dying or hiding underground, wetland plants can flower en masse.

Purple Loosestrife (Lythrum salicaria) and Slender Knotweed (Persicaria decipiens) are both easy to grow, and provide a lot of nectar and pollen for butterflies, day-flying moths, and bees. These species include the Common Blue Butterfly, the Ochre Skipper Butterfly and moths from the Agaristinae family. Additionally, Purple Loosestrife is a haven for Blue-banded, Resin, Chequered Cuckoo and Leafcutter Bees. These bees not only pollinate wetland plants, but will also pollinate other plants in the vicinity. In my backyard, Blue-banded Bees are visiting my wetland, herb garden (Catnip, Lemon-balm, Mint), and tomato plants - pollinating as they go.

A rather interesting observation I've noted is the amount of white flowering plants you see in wetlands - examples include Water Plantain (Alisma plantago-aquatica), Australian Gypsywort (Lycopus australis) and Willow Herb (Epilobium billardierianum). Some studies have shown that white and yellow flowers tend to be visited by a larger range of insects. Having white flowers in high summer, when flowering diversity is low, makes sense for an insect-plant relationship because many insects will happily feed from these plants.

A Chequered Cuckoo Bee feeding on Purple Loosestrife.  Image: Michael Smith

A Chequered Cuckoo Bee feeding on Purple Loosestrife. Image: Michael Smith

With so much insect diversity around wetlands, it is no wonder predatory arthropods feel at home around these water bodies. St Andrews Cross Spiders make their webs between Carex leaves, waiting for insects to become trapped, while dragonflies and robber flies search the wetland zone for small insects, such as mosquitoes, to feast on.  

If you're interested in creating a wetland in your garden, there are many good examples online and in council booklets. Wetlands can be made from baths or depressions with a lining. If you're looking for a terrestrial plant that can handle dry soil in summer, then Sweet Bursaria (Bursaria spinosa) is of great value. Their long, deep roots allow them to locate water in places other plants cannot reach. At times I've seen these trees teaming with bees, flies, butterflies and beetles. It comes as no surprise that this plant also has white flowers.

Michael Smith is a trained ecologist who currently works in bush regeneration, habitat engineering and environmental education. He is passionate about community engagement and teaching the importance of biodiversity.

Banner image of Alisma plantago-aquatica courtesy of Christian Fischer [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons


Bladderworts: Wildflowers of the Wetlands

This is a guest post by Mackenzie Kwak.

As we Melburnians sweat through the last of summer’s heat, many of us seek refuge in the cooler and damper places around our city. Although less commonly visited, the Greater Melbourne region boasts an array of magnificent wetlands, and these warm periods are the perfect time to see some of our most magnificent wildflowers of the wetlands: the bladderworts.

Bladderworts are poorly known plants, owing to their small size and often brief flowering periods, which commonly occur during our warmer months when the urge to venture into wild places is often quelled by a brief glance at the thermometer. They are, however, some of the prettiest wildflowers that can be seen over the summer and also exhibit one of the rarest and most remarkable traits amongst plants: carnivory.

Being typically confined to damp places has not limited the spread of bladderworts across the globe. Today, bladderworts are found on every continent except Antarctica. Globally there are more than 200 species recognised, of which 10 can be found in Victoria. These species can be seen all through the state, flowering and growing from early spring through to autumn, depending on the species.

  The aptly named redcoat ( Utricularia menziesii ).

  The aptly named redcoat (Utricularia menziesii).

A vibrantly coloured fairy apron ( Utricularia dichotoma ).

A vibrantly coloured fairy apron (Utricularia dichotoma).

What is truly remarkable about bladderworts is their strange way of life. As they often grow in nutrient-limited habitats such as wetlands, seeps and ditches, they have developed the ability to trap and digest prey. The name bladderwort comes from the Middle English word ‘wort’ meaning plant, and ‘bladder’ which refers to the little traps that adorn their green stems.

The traps of bladderworts are very cleverly adapted to catching prey and consist of a round bladder with a small opening at the end, covered by a tiny trapdoor and a small trigger hair. Any water within the closed bladder is pumped out by the plant which creates a vacuum within the trap. When a small animal moves past and touches the trigger hair, the trapdoor is opened and the vacuum causes anything directly surrounding the trap, including the hapless creature, to be sucked in, where it is digested. Due to their small size, bladderworts feed on smaller quarry than some of Australia’s more commonly known carnivorous plants like sundews. Bladderworts are specialists of pondlife, creatures ranging in size from the near-microscopic paramecium all the way up to mosquito larvae.

Melbourne’s bladderworts can loosely be divided into two groups: the terrestrial species which produce tiny leaves and often live on the damp earth around wetlands or along seeps, and the aquatic species which are free-floating and grow at the warm surface of wetlands and lakes. Both groups are extremely well adapted to our conditions. Some species live as annuals, flowering during warm wet periods and producing copious amounts of seed before their little ponds dry up. Some live as perennials and form little buds which sink to the bottom and are buried in the mud as their wetlands dry up over the hottest part of summer. Still others sometimes occupy permanently flooded wetlands and grow all year round.  

Amongst those enthusiastic about growing plants, particularly carnivorous plants, bladderworts are a popular choice. Many species are very easy to grow and will flower prolifically under the right conditions. However, it must be stressed that removing plants from the wild, although seemingly tempting, can contribute to the local extinction of some populations and is illegal in protected areas. Many wild-collected plants also often die upon removal from their habitats. There is a wide array of inexpensive and lovely native as well as imported exotic bladderworts that can be purchased from specialist nurseries or through dedicated societies for those interested in growing these beautiful plants at home.

A perennial, aquatic species of bladderwort ( Utricularia australis ).

A perennial, aquatic species of bladderwort (Utricularia australis).

So whether you are now keen to go out and catch your first glimpse of these remarkable wildflowers or want to give growing them at home a try, bladderworts never cease to fascinate people and will likely captivate you as well.

For more information, visit the website of the Victorian Carnivorous Plant Society.

Those looking to grow these remarkable plants should visit Collectors Corner or contact Triffid Park Nursery.

Mackenzie Kwak is a zoologist with a broad interest in Australia's diverse flora and fauna. His research focuses on the biogeography, systematics and ecology of Australasian ectoparasites, particularly ticks, fleas and lice. 

All photos sourced from Wikimedia Commons.

Life of the City: A Short History of the Yarra River

Before dawn, under a soft scattering of clouds, the Yarra River is still and silent. Most mornings the sight goes unappreciated by the majority of Melburnians – shared only by joggers, rowers and the early commuters who pass along the banks. The sky upriver is slow to warm, splashing orange and gold across the tallest city buildings until the day opens with a flash.

Sunrise over the Yarra River.  Image: Paul Jones

Sunrise over the Yarra River. Image: Paul Jones

The banks of the Yarra are a major drawcard for residents and tourists alike. From the 1980s, extensive cleaning, replanting and developing have created a new urban precinct with admirably natural features. During the rest of the 20th Century, the river was notorious for the detritus of industry and the pollution of suburban runoff. Now, fresh beds of wetland plants line the river’s edge; swans, egrets and cormorants call and fly from the nearby refuges of Herring Island and the Botanic Gardens; rubbish traps collect the worst of the upstream spillage.

The thing is, these natural features aren’t very natural at all. The shaping of the Yarra – widening, straightening, grading – has led to a much more stable river course than what was originally present. Water from storms is filtered and driven into the bay along bluestone-lined banks. Upriver, dams and weirs keep the catchment rains and spring snowmelt in check as they tumble out of the mountains above the Yarra Valley. Nowadays, it takes the heaviest downpours to show unsuspecting people just how the landscape originally functioned.

Journalist Neville Bowler's iconic photo of the Elizabeth Street flood.   Image: Neville Bowler

Journalist Neville Bowler's iconic photo of the Elizabeth Street flood. Image: Neville Bowler

A winter flooding in 2014 saw the river leave its banks behind and inundate waterfront businesses, saturating social media with images and stories. Cultural memory recalled a similar event, when the tributary creek sealed beneath Elizabeth Street spectacularly resurfaced in 1972 after heavy rains – perhaps the first time that many were given cause to consider the reason for the street’s low-lying topography.

Before European alteration, however, these events would not have been isolated quirks. The floodplain of the Yarra and Maribyrnong Rivers is home to an ecosystem that thrived on annual deluges, with the iconic river redgums (Eucalyptus camaldulensis) requiring spring floods to stay healthy. Each year, thawing snowfields would deliver a torrent of water through the Yarra Valley (its own floodplain now the location of fertile vineyards) down to Port Phillip Bay, recharging the soil and enriching those extensive wetlands of which Albert Park Lake is one final remnant. There is also evidence from other Australian sites that this cycle can prevent salinity from building up in the soil, having a direct impact on which plants could grow in the area and which animals could reside.

Floodplains rely on variability to maintain a patchwork of ecosystems, both temporally and spatially. Australia’s climate creates an especially changeable environment, with low rainfall leaving many parts of the region dry through the majority of the year. Their occasional submersion led to an eruption of germinating seeds and rapid new growth. Closer to the river, the more stable water supply allowed softer plants to grow and encouraged amphibians and birds. In contrast, the unchanging conditions of modern engineering favour some groups while stressing others, and can eventually lead to a loss of biodiversity.

Apart from the regulation of flow, other changes have affected the vegetation along the riverbanks as well. The slow-flowing surface of the river is undercut by a wedge of heavy salt water from Port Phillip, creating a saline gradient that runs well upriver. Unexpectedly, this common estuary pattern has only made a relatively recent appearance in the Yarra’s dynamic. It’s been that way since the 1880s, when a natural ford damming the Yarra downstream of Queen Street was blasted away to build the bridge that still stands.

Historically, the river was completely bifurcated by this rock formation, to the great advantage of the Wurundjeri tribe who took care of the land. Freshwater from upriver was retained en masse, ensuring a secure drinking supply that was kept separate from the saltwater of the bay. Eels and other fish were abundant in the region, along with birds arriving for the same purpose. The ford, and the waterfall it created, would also become a pivotal component in the decision of European settlers to start building; the deep, wide basin drummed into the riverbed below the falls was ideal to be used as a turning circle for cargo ships visiting the new city.

A downriver view of the original Yarra course, with the rock wall visible in the centre.   Image: http://ergo.slv.vic.gov.au

A downriver view of the original Yarra course, with the rock wall visible in the centre. Image: http://ergo.slv.vic.gov.au

Changing the water from fresh to brackish meant that vegetation along the banks needed to cope with much higher amounts of salt, leading to community restructuring and a general reduction in quality. But while the upstream basin was significantly changed by saltwater mixing, it arguably couldn’t have been made much worse. Industries springing up in 19th Century Abbotsford and Collingwood, along with the suburbs encroaching along both banks, meant that an incredibly high level of sewage and commercial waste travelled directly into the river. At this point, the river was still being used as drinking water for the city, leading to chronic outbreaks of waterborne diseases. Continuous clean-up and revitalisation campaigns through the last century have improved matters, but the river still contains high levels of bacteria and heavy metals.

The unavoidable fact is that, like most metropolitan rivers in the 21st Century, the Yarra is at the mercy of the community around it. But it can also influence that community – as something so very visible in Melbourne, the river is uniquely positioned to remind us that our actions aren’t separate from the world around us. The new plantings along the riverbanks remind us that we can restore habitat if we try; the rubbish traps show us that waste removal doesn’t need to be complicated to work (as well as remind us to be more careful); the calling birds reward us by returning to the spaces we’ve made for them. As long as the river keeps flowing, it can be changed – one way or another.


Paul works in science education and has been a teaching member of Monash University's Department of Biology since 2010. He is interested in community engagement and sustainable urban development.

Banner image courtesy of Paul Jones. 

Valuing our Ecosystems: The Role of Wetlands

Have you ever found yourself admiring the calls of ducks, the croaking of frogs across a lake, or the swaying of reeds while walking your dog at your local wetlands? Have you wondered how wetlands are able retain to water for such long periods of time, or been awed by the myriad of wildlife you’ve encountered in their vicinity?

Wetlands are amazingly diverse habitats, home to thousands of different species worldwide. However, according to the most recent scientific studies, 64% of the world’s wetlands have disappeared since 1900 and 76% of freshwater plants and animals have disappeared in the last 40 years, making them among the most vulnerable of ecosystems.

The Murray River at Swan Reach in South Australia. The wetlands have dried up as the flow of the water has reduced.  Image: Murray Darling Water Authority.

The Murray River at Swan Reach in South Australia. The wetlands have dried up as the flow of the water has reduced. Image: Murray Darling Water Authority.

One of the reasons for this is that wetlands are increasingly being targeted for land reclamation and conversion into agricultural, industrial and urban areas. Yet, they play a much bigger role in the ongoing prosperity of our communities, and this is something worth discussing. So, what value do our wetland habitats offer?

The Importance of Wetlands

Wetlands are areas of land that are saturated or flooded with water, either permanently or seasonally. There are many kinds of wetlands including both inland wetlands such as marshes, ponds, lakes, fens, rivers, floodplains and swamps, as well as coastal wetlands, such as saltwater marshes, estuaries, mangroves, and lagoons. The size of wetlands also varies dramatically, from less than a single hectare (around the size of your local lake) to the Pantanal in Brazil, Bolivia and Paraguay, which covers an area three times the size of Ireland.

Thousands of different species of birds visit wetland areas to breed.  Image:   CSIRO. 

Thousands of different species of birds visit wetland areas to breed. Image: CSIRO. 

Wetlands are home to more than 100, 000 known freshwater species and this number is growing all the time. Between 1999 and 2009, some 257 new species of freshwater fish were discovered in the Amazon alone. Wetlands in Australia also provide breeding grounds for up to 2 million migratory birds that travel thousands of kilometres for their annual breeding migration.     

The red-necked stint is a   small migratory bird that nests in the Siberian tundra before traveling thousands of kilometres to reach Australian shores. After a six month break, it then makes the return journey back to Siberia to breed.   Image: Wikimedia Commons

The red-necked stint is a small migratory bird that nests in the Siberian tundra before traveling thousands of kilometres to reach Australian shores. After a six month break, it then makes the return journey back to Siberia to breed.  Image: Wikimedia Commons

A Crucial Role in Mitigating Climate Change

Aside from providing a habitat for wildlife, wetlands are also known to provide other ecosystem services such as reducing erosion and flooding, improving water quality, and, notably, playing a crucial role in mitigating the impacts of climate change. In particular, peatlands (areas with a thick, water-logged, organic soil layer) act as a key means of carbon storage. Globally, peatlands only cover an estimated 3% of the world’s land area, but hold up to 550 gigatonnes of CO2 - approximately 30% of all carbon stored on land. Amazingly, this is twice the amount of carbon stored in the world’s forests - not what you would expect, right? They therefore serve as vital areas to protect when tackling climate change.

Peatlands in Forsinard, United Kingdom.    I    mage:   RSPB   .

Peatlands in Forsinard, United Kingdom. Image: RSPB.

In spite of this, warming temperatures as well as human development are threatening these habitats as they are burned, drained for agriculture, or exploited for oil and gas deposits. Consequently, they are being transformed from carbon sinks to carbon sources. According to Wetlands International, CO2 emissions from peatland fires equate to a staggering 5% of all annual fossil fuel. Furthermore, in Indonesia, emissions from peat soils due to logging and drainage contribute 60% to their total CO2 emissions (~900Mtons per year).

Finding a Balance

In a world that is undergoing both dramatic environmental and economic changes, decisions concerning the development of  native ecosystems are becoming increasingly difficult. In another article published by Wild Melbourne, the idea that half of the Earth must be ‘given’ to nature in order for it to continue to thrive is presented as a potential solution to the modern environmental crisis. When we consider all that wetland ecosystems do for us, their dramatic fall into degradation, and our rising global population, it is definitely a conversation worth having.

We know that just considering what the environment can provide for us in the short term is not a sustainable method of making these decisions. Perhaps, we need to ask ourselves what role the environment is already playing and whether we have placed sufficient value on those services. Only then can we begin to form a holistic and balanced approach to economic development that acknowledges the role of our wetlands and other ecosystems in both our present and future.  

Banner photo courtesy of CSIRO.