24 September 2018
Last week Hub researcher Vanessa Hernaman and knowledge broker Mandy Hopkins travelled to Shark Bay in Western Australia to participate in a workshop to lay the foundations for developing a climate change adaptation plan for the World Heritage Area. They joined representatives from the Western Australian Department of Primary Industries and Regional Development and Department of Biodiversity, Conservation and Attractions as well as Bush Heritage, the University of Western Australia and the Western Australian Marine Science Institution to identify how climate change will affect the region, and the impacts this could have on the region’s natural assets.
A site of global significance
World Heritage properties are sites of global natural or cultural significance, to be preserved for the future on the basis of their outstanding universal value (OUV). Each listed property has a statement of OUV that documents the attributes and values that led to the original listing and that serve as a basis for monitoring and management.
Shark Bay was listed as a World Heritage Area in 1991 and is one of 19 World Heritage Areas in Australia. To be listed as a World Heritage Area, properties must meet at least one of 10 criteria (four natural criteria and six cultural criteria). There are 1092 World Heritage sites listed worldwide, 209 of which are listed for natural criteria only. Of these, only 21 – including Shark Bay – meet all four natural World Heritage criteria:
- Exceptional natural beauty
- Examples representing major stages of Earth’s history
- Examples of significant ongoing ecological and biological processes
- Important and significant natural habitats for conservation of biodiversity.
Stromatolites, seagrass and salinity
Shark Bay is possibly best known for its stromatolites – structures built up by living microbial colonies. Stromatolites in the fossil record date back 3.7 billion years ago, so the Shark Bay stromatolites at Hamelin Pool provide a rare glimpse into the evolution of life on Earth.
The area is also home to one of the world’s largest seagrass meadows, with the most seagrass species recorded from one area. As well as providing food and habitat for myriad marine species – including nearly 10% of the world’s population of dugongs – the seagrass beds and underlying sandbanks contribute to the hypersalinity of Hamelin Pool, and so to the existence of the stromatolites.
Turtles, sharks, rays and dolphins – including the famous Monkey Mia dolphins – live in the Bay, which also sustains significant fisheries and marine invertebrates. The area is also rich in terrestrial flora and fauna, including four species of mammal (Shark Bay mouse, western barred bandicoot, banded hare-wallaby and rufous hare-wallaby) that are not found in the wild anywhere else.
Climate change vulnerabilities
Workshop participants considered how the values and attributes comprising Shark Bay’s OUV could be impacted by a changing climate, drawing on events such as the 2011 marine heatwave as examples of extreme climate events that may become more frequent.
Sea-level rise, reduced rainfall, intense storms and higher air and sea temperatures all have the potential to tip the balance of biological and physical systems in this unique region, as do coincident events. An example – already observed in 2011 – is the occurrence of a marine heatwave along with sediment deposits from flooding due to heavy rainfall. The combination of elevated temperatures and lack of light from the sediment in the water resulted in a significant dieback of seagrass.
The ongoing integrity of seagrass in Shark Bay not only poses a threat for species that rely on it directly but also on the stromatolites. The seagrass and underlying sandbars help maintain the hypersaline environment of Hamelin Pool. Sea-level rise, wind changes and increased run-off could all change the salinity in the pool, changing the conditions that allow the stromatolites to flourish.
Planning for the future
The Earth Systems and Climate Change Hub will be working with the Shark Bay World Heritage Advisory Committee to use climate change projections to assess the climate risk to Shark Bay’s seagrass species. This information will be an important component of the climate change adaptation plans for Shark Bay.