On Hexham Swamp with Cameron Webb

“I personally think the potential impacts coming to our coasts due to sea-level rise and extreme storm events aren’t fully appreciated.”

I encountered Dr. Cameron Webb’s scientific work through his music — specifically a 2010 collaborative album with Matt Rosner called Two Lakes, which contains field recordings from Meroo and Termeil lakes, a pair of fragile coastal ecosystems. It was immediately clear to me that this could only be the product of a person with a deep understanding and appreciation of the Australian wilderness, so it was not a great surprise to learn that Cameron’s connection to the environment appears in all aspects of his life. Not only does he continue to make music under the name Seaworthy, but he is also a nature photographer, a passionate water advocate who spends his leisure hours paddling down the Paramatta River, and a reputable entomologist who spends his working days knee-deep in the mud of local wetlands, from Dora Creek to Kooragang Island.

The primary focus of Cameron’s work is on mosquitoes and so I spoke with him about the facts and myths of this frequently encountered yet little understood species, as well as the fascinating ecology of swamplands and the increasing threat of urban development on our coasts.

Fieldwork on the tidal flats of Ash Island

Do you have any early memories of visiting wetlands or simply having an awareness of them?

As a young boy I spent a lot of time walking around sedgelands on the south coast of NSW. Many of the lakes and lagoons there are bordered by sedgelands and occasionally flooded she-oak woodlands. These are essentially the same habitats I visit now for my work. I love coastal heath environments but the tidal lagoons and associated wetlands are probably my favourite places to spend time in.

What was it that got you interested in ecology in the first place?

Not so much ecology but a career in science was probably prompted by an early interest in the weather and tidal cycles. As a keen surfer, I learnt the role of tides and wind in making for great conditions and also how the synoptic chart printed in the daily newspaper could help forecast what the surf conditions would be like in the days ahead. This was a long time before surfers had swell-predicting apps on their phones. I did work experience at the Bureau of Meteorology in Sydney when I was about 14 and for a while there I thought that I had a career path heading in that direction.

It wasn’t until attending Macquarie University, to do a degree in Environmental Science and Management, that I was introduced to the field of ecology. At the time, there was a real focus on the use of ecology to assist environmental impact assessments and the idea of using data on insects, frogs, or birds, to assess the current health of the environment and forecast its future was fascinating. I volunteered to assist a few PhD students who were undertaking various forestry projects and was hooked.

Initially, your research was focused on coastal sand dunes what was the interest there, and what did your work involve?

My first research project was undertaken as part of my BSc Honours degree. I’d always been mindful of the sand dune restoration projects on the NSW South Coast. Within my lifetime I had experienced an incredible decline in the size of dunes and saw numerous measures taken to try and stabilise them. One such measure involved an exotic grass species that was used to stabilise the dunes with the idea being that the grass would provide a quick fix which would then, over time, be replaced by native grasses, shrubs, and trees that were slower to establish. However, in many areas, the exotic grasses persisted. My project was to look at insect populations, especially ants, in sand dunes that had been naturally vegetated and compare them to those being rehabilitated. It was a fascinating introduction to ecological research, I often think about revisiting those sites 20 years later to see how much has changed.

What shifted your interest towards wetlands?

During the BSc Honours degree I also undertook a project on frogs in Western Sydney. The project was looking at how the spread of an exotic fish — known as the plague minnow or mosquitofish — was impacting frogs in farm dams and other wetlands around the Kellyville, Castle Hill, and Rouse Hill region of Sydney. I demonstrated that the fish were having an impact, but, two decades later, most of those areas are now under incredibly dense urban development. Seems the fish weren’t the biggest threat to the frogs! I enjoyed working in the wetlands and I haven’t been able to escape them yet.

The widespread vector mosquito, the Skuse (Aedes vigilax)
A local species, the Hexham Grey (Ochlerotatus alternans)

Your work is now primarily focused on mosquitoes, a diverse group of small fly species that are incredibly common in Australia yet widely misunderstood. What makes this insect so interesting to you and what is its role in the wetlands ecosystem?

For the past 25 years I’ve been working with mosquitoes. They’re the deadliest animals on the planet, the pathogens they spread kill almost a million people every year, and hundreds of millions of people are infected. But mosquitoes are also fascinating. They have a complex life cycle that involves eggs and immature stages associated with aquatic habitats. These aquatic habitats can be incredible variable but the mosquitoes are highly specialised. Some mosquitoes prefer saltwater conditions, others freshwater. Some are highly tolerant of polluted water while others like to live in water-filled tree holes or rainwater tanks. From snowmelt streams in alpine regions to coastal rock pools, there are mosquitoes found everywhere. This diversity is probably one of the things that keep me fascinated with them. If you give me a collection of mosquitoes, I can reasonably confidently describe the landscape from where they were found.

Scientists are good at working out how to kill mosquitoes and understanding how they spread the pathogens that make us sick. However, we haven’t been great at working out their ecological role. We know they provide food for frogs, spiders, insects, reptiles, birds, and mammals. We know they pollinate plants. But there is yet to be a plant or animal on the planet that has been found to be completely reliant on mosquitoes to survive.

What about the ways in which they have adapted to urban environments?

Mosquitoes are incredibly adaptive animals. A not-so-great example of this is how mosquitoes have adapted to life in and around our homes. There are mosquitoes that evolved to live in the leaf axils of plants but now they’re happy living in potted plant saucers, blocked roof guttering, discarded plastic bottles, and our rainwater tanks. While the Australian backyard mosquitoes are serious nuisance-biting pests, there are some mosquitoes in the world, such as the yellow fever mosquito or tiger mosquito, that have adapted to these environments in many tropical and temperate regions of the world. Their ability to spread a wide range of pathogens and propensity to bite humans means they can drive major outbreaks of mosquito-borne disease. 

What does your work in mosquito surveillance involve?

In short, it essentially involves the sampling of mosquito populations around wetlands. Whether we are sampling adult mosquitoes or immature mosquitoes will depend on the nature of the wetlands and the objectives of the surveillance program. Sometimes it is about tracking changes in mosquito populations over the seasons, other times it may be about assessing how changes in wetland management or mosquito control programs are influencing the pest and public health risks associated with mosquitoes.

To collect mosquitoes, we use quite primitive-looking traps. They are essentially a ‘billy can’ with a motorised fan and bucket hanging below. They’re basic but incredibly effective. We bait them with carbon dioxide (usually dry ice) and that attracts the female mosquitoes that use carbon dioxide to find an animal to bite. Tricked into approaching the trap, the fan sucks them into a collection bucket. Unlike the types of ‘light traps’ other entomologists may use, these traps are highly specific to mosquitoes and so are less likely to collect moths, beetles, and other flying insects. By comparing the diversity of mosquitoes collected, we can make an assessment on the likely pest and public health risks in a local area.

What are some of the biggest misconceptions about mosquitoes?

There isn’t an appreciation of the incredibly diverse number of mosquitoes we have in Australia. There are more than 300 species with many yet to be formally described. The vast majority pose very little threat to people: either they don’t bite humans at all, perhaps preferring birds or frogs, or are unable to spread the most serious disease-causing pathogens. Sometimes mosquitoes are found in such a highly specialised ecological niche that they’re just unlikely to be a problem for anyone. Once you get a mosquito under the microscope you discover that they are actually quite beautiful. Their bodies are covered in intricate patterns of scales and bristles. Some species are almost iridescent in colour.

Wetlands mosquito trap in use

What are some of the health issues related to mosquitoes?

Internationally, diseases such as malaria and dengue are of greatest concern. There are hundreds of millions of people across Asia, Africa, South America, and the Pacific that are at risk. These diseases can be seriously debilitating and, in the case of malaria, deadly. There are other viruses of concern such as Japanese encephalitis, West Nile, and chikungunya viruses. In 2016, the outbreak of the Zika virus in Central and South American almost caused the Rio Olympics to be canceled.

In Australia, the Ross River virus is the mosquito-borne pathogen of greatest concern. About 5,000 people are reported each year having been infected but that is probably an underestimate given many people will experience mild symptoms and won’t get tested and appear in official statistics. While Australia is generally free of the more serious global pathogens, we do have the very rare but potentially fatal Murray Valley encephalitis virus present and it is a concern in northern Australia. 

When is mosquito season and how can people living near waterways and swampland better prepare for it?

Some mosquitoes are active all year round, it’s just that they’re in such small numbers and not nearly as active as the warmer months that we tend not to notice them. We’ll start to see some of the pest mosquitoes active in early spring and they can persist through to early winter. It’s the activity at either end of that period that can change with local conditions. Cooler and drier weather will tend to result in fewer mosquitoes. During most years, the period from December to the end of March is when mosquitoes are consistently most active. There wouldn’t be an Australian summer without mosquitoes but there can be some summers when mosquitoes numbers are almost unbearable. The numbers of mosquitoes are primarily determined by seasonal rainfall patterns, but also tides. If we’re particularly unlucky, heavy rain and high ‘king’ tides can occur during December and kick off a momentum of mosquito population rise which means they can be problematic for months.

Another key focus of your work is the critical issue of urban planning on wetlands and coastal areas. Where are the most urgent issues here and how can we better plan for climate change, rising sea levels, and the preservation of these endangered ecosystems?

Everyone wants to live on the coast, however, this demand not only increases impacts on coastal wetlands through pollution, physical damage, and the introduction of feral animals, but it traps these wetlands and makes them vulnerable to the impacts of climate change and sea-level rise. Coastal wetlands are incredibly adaptive. Plants and animals adapt to changes in sea level and respond rapidly to extreme weather events. The problem is, our urban development has not allowed any capacity for these wetlands to change in response to sea-level rise. They’re trapped by housing, industry, and associated infrastructure such as sea walls, roadways, and other obstructions. Over the past two hundred years, we’ve also reclaimed land for housing, industry, and agriculture by modifying tidal flows and drainage patterns. What true wetlands actually remain are often in poor ecological health and it has only been in recent decades that the value of wetlands has been understood as not just habitat for plants and animals, but for the health and well-being of people as well as carbon sinks to assist in managing the impacts of climate change. For these reasons, authorities around the country, particularly in the Hunter region, have been working hard to rehabilitate degraded wetlands, protect existing wetlands, and create new wetland areas that can be integrated into urban development plans. Mosquitoes are often a symptom of the poor ecological health of these wetlands and, unfortunately, simply building a wetland and undertaking poor planning decisions around wetland management can increase pest mosquito populations. A lot of my work is assisting authorities in better design of the planning, construction, and management of wetlands so that mosquito populations are minimised. We don’t want to eradicate them, they’re as much a part of the coastal wetland ecosystem as fish and birds, but we want to keep their numbers to tolerable levels.

Hexham in flood, 1893
Ironbark Creek in flood, 1893

While you conduct your work all over the state, you frequently visit Hexham Swamp, known to local Aboriginal people as Burraghihnbihng. Could you talk a little about this area, its heritage, its present condition, and perhaps what you see for its future?

Hexham Swamp, as well as the surrounding wetlands of the Hunter River, are wonderful. The Hexham Swamp Rehabilitation Project is one of the most significant environmental and ecological rehabilitation projects in Australia and it has been a pleasure to see the changes in the area over time. Decades ago, to assist flood mitigation and enhance agricultural areas along the river, tide gates were installed that prevented the flow of tidal waters from the Hunter River in the surrounding wetlands. The area transitioned to a freshwater-dominated environment. The area of heavily grazed and extensive areas of reeds (Phragmites australis) dominated the site. When I first visited the site, there were a few remnant mangroves, stunted at best but mostly dead. There was very little wildlife. In recent decades, considerable effort has been put into restoring tidal flows to the wetlands by opening floodgates at various locations, especially Ironbark Creek, which has allowed an incredible transformation of the wetlands. It had been a few years since I’ve visited but I returned in the 2019-2020 season and it was spectacular. There are thriving saltmarsh and mangrove areas and the birdlife appears to be flourishing. Ongoing management will remain a challenge but, for now, it is wonderful and I hope in the future the area becomes more accessible to the general public. 

As someone who spends so much time on our coasts and waterways, both professionally and recreationally, what is your present outlook on their futures?

I personally think the potential impacts coming to our coasts due to sea-level rise and extreme storm events aren’t fully appreciated. It would appear that the impacts of heatwaves, bushfires, and flooding is now more frequently front-of-mind for much of the community, but for coastal impacts, I’m not sure there is as strong an appreciation. There are clearly regions of Newcastle, Central Coast, and Sydney’s Northern Beaches where erosion is already significantly impacting the coastline and putting residential properties and infrastructure in danger. This is only going to continue. The subtle impacts on wetlands are probably overlooked even more so. Many of our coastal wetlands rely on subtle changes in inundation and drying and with sea-level rise, they’re staying too wet and not salty enough to maintain healthy ecosystem function. There are some wonderful coastal scientists doing work in this field but we need more, or at least more available research funding, to ensure monitoring and research continues.

Categorized as Seafolk
Heath Killen

By Heath Killen

Heath Killen is the founder and editor of On A Floating World. Born and raised in Newcastle, he is passionate about the coastline and waterways surrounding his home. Elsewhere he helps people develop brands, campaigns, and projects based on their passions.