Advancing our understanding of blue carbon science

Kerrylee Rogers wears many hats. She’s a Professor in the School of Earth, Atmospheric and Life Sciences at the University of Wollongong, a passionate advocate for environmental sustainability and the mum of two teenage boys. She’s made a significant contribution to our understanding of how coastal and aquatic ecosystems respond to climate change, work that earned her and her fellow researchers the 2019 Eureka Prize for Environmental Research. We caught up with Professor Rogers to chat about what sparked her interest in the natural sciences, the implications of her research and empowering the next generation.

Can you tell us a little bit about where your interest in environmental sustainability began?

I grew up on the south coast of New South Wales and spent a lot of time having exciting adventures with my sisters and cousins in and around Jervis Bay, where all my grandparents lived. I had such a fantastic time and I think this sparked my interest in the natural sciences and environmental sustainability. I’m still happy to traipse around the shores of Jervis Bay and St Georges Basin, but now I get to call it ‘work’. These days, I’m aware that the coast is where the land meets the sea, and where geology meets ecology and hydrology; it’s such a diverse and multidisciplinary space to be working in and this suits me perfectly.

Much of your research focuses on the response of coastal and aquatic ecosystems to climate change. Can you talk us through some of these responses?

As I mentioned, the coast is the interface between the land and the sea, and it’s not surprising that variation in sea level — whether due to tidal fluctuations, storm surges, climatic variability or human induced climate change — has a significant influence on the morphology of the coast and the distribution of coastal ecology. Coastal wetlands such as mangrove, saltmarshes and coastal floodplain forests are front and centre of this interface, occupying a ‘narrow niche’ within the intertidal zone.

Sea level has already been rising around the Australian coast, estimated to be in the order of about 25 centimetres since 1880, and accelerating sea-level rise is one of the most profound impacts of human induced climate change. Sea-level rise will force humans to adjust to the new form of the coast, and actions typically ascribed as protecting assets, adapting to the altered conditions or retreating from the risk.

Sea-level rise will also impose similar responses on coastal ecosystems. These coastal ecosystems can adapt to the increase in water levels associated with sea-level rise by increasing their elevation, allowing them to maintain their position with respect to sea level; this is achieved largely by accumulating sediments and organic material from vegetation within their substrates. Alternatively, they can retreat to higher elevations, and this will largely result in changing distribution of ecosystems — we are already seeing this pattern of change with mangrove forests beginning to retreat to higher elevations that are typically occupied by saltmarshes. Protection of coastal ecosystems is largely a human response that’s intended to improve their capacity to either adapt or retreat. Our actions, such as creating protected buffer zones around coastal ecosystems that will serve as future pathways for retreat, will be critical.

Some readers may wonder why we would be so concerned about the response of coastal ecosystems to sea-level rise; well, it’s because they provide a lot of goods and services that are of direct benefit to humans. Commonly termed ‘ecosystem services’, or ‘nature’s contributions to people’, these benefits include wildlife habitat and food sources for a range of biota including commercially important species, coastal protection services achieved by buffering wave action and binding sediments, nutrient and carbon cycling services and many other benefits that have both social and economic benefits. Carbon sequestration services, for example, are receiving considerable interest now due to the need to mitigate climate change and coastal wetlands can be, under the right conditions, particularly efficient at delivering on this service.

The Eureka Prize-winning research you led revealed that coastal wetlands are incredibly effective at capturing carbon dioxide from the atmosphere. What have been the implications of this finding?

Blue carbon — ­carbon captured by the world’s ocean and coastal ecosystems — plays a significant role in climate change mitigation, and blue carbon science has advanced considerably in the past few years. The uptake of knowledge is increasing and I like to think that the research we undertook played a role in this. Very recently, the Commonwealth Government of Australia, through the Clean Energy Regulator, developed a blue carbon methodology within the Emissions Reduction Fund that provides the framework for granting Australian Carbon Credit Units (ACCUs) for carbon sequestration in biomass and soils, and avoided emission from the restoration of coastal wetland following tidal reintroduction.

ACCUs can be traded back to the government or to a third party to offset their emissions, and are intended to contribute towards Australia’s efforts to mitigate climate change. The work we undertook demonstrated the role of sea-level rise as a driver of blue carbon storage within wetlands, and it provided evidence of potentially many opportunities for coastal wetlands within Australia and across the southern hemisphere, to respond to sea-level rise by sequestering carbon within soils and biomass of coastal wetland vegetation. Facilitating an ecosystem response to sea-level rise could generate ACCUs – which is a better outcome than protecting the coast from sea-level rise and preventing adaptation by coastal ecosystems.

This work effectively increased confidence that blue carbon generated as sea level rises and as coastal wetlands retreat, would be resilient and provide the necessary permanence (minimum of 25 years) for a blue carbon methodology to be viable. The next step will be to see broadscale uptake of the methodology and further methods developed that focus on activities that facilitate adaptation to sea-level rise, such as land-use change from agriculture to coastal wetland.

What are some of the larger impacts you hope to see from your work in the future?

The blue carbon methodology within the Emissions Reduction Fund focused initially on tidal restoration activities, but I would like to see the method expanded to consider the blue carbon additionality that occurs as coastal wetlands adapt to sea-level rise, particularly via retreating to higher elevations. This would require a method allowing ACCUs to be provided when an activity is undertaken that facilitates adaptation to sea-level rise, and would include activities that remove any barriers to the natural adaptation response of coastal wetlands to retreat, such as incompatible land-use — for example agriculture.

In many cases, sea-level rise will impose a land-use change, particularly on low-lying agricultural land on coastal floodplains, which may already have limited viability — opportunities we’ve already started identifying. The larger impact of a sea-level rise methodology could be a shift in the way coastal floodplains are managed with an increasing focus on ‘working with nature’ to provide blue carbon services, and many other co-benefits. This shift differs to the prevailing approach to coastal management of ‘holding back the tide’ and will be critical if sea-level rise accelerates as projected; holding back the tide cannot be effectively applied across the broad coastal floodplains of the vast coast of Australia, and cannot occur indefinitely — a different management approach will be needed.

As a mother, how are you educating and empowering the next generation when it comes to environmental sustainability?

I am very passionate about environmental sustainability and hope that I’m passing this on to my own children. My two teenage boys are both very active and heavily involved in outdoor activities (as I was as a child), and I anticipate that their awareness of the natural environment is growing. They playfully tease me about this passion, as teenage boys would do to their mum. Nevertheless, I‘m acutely aware that we are failing the next generation by passing on a world littered with environmental mismanagement, and as an outcome, I’m persistent and know some of it is sinking in.

As the academic program director for the University of Wollongong’s environmental science program and a supervisor of postgraduate students, I’m in the fortunate position of also influencing the next generation of environmental scientists. The director role, in particular, is incredibly rewarding as I get to witness fresh, aspiring first-year scientists increase their knowledge and nurture passions for the natural environment, and ultimately achieve their own goals of improving environmental sustainability.

Has winning a Eureka Prize resulted in any unexpected opportunities?

Well, it still surprises me when I’m at a meeting and get introduced as a “Eureka Prize-winning environmental scientist”. There’s so much great environmental science generated in Australia, and I still need to pinch myself that we received this award. The immediate increase in my profile and that of the team was, without a doubt, a fantastic outcome (and why others should apply for the prize) and has really strengthened our collaboration. This enhanced profile has definitely increased opportunities for collaboration, both in Australia and internationally, which will allow us to continue making progress towards improving coastal management.