Torres Strait seagrass meadows are among the world’s largest, covering over 13,000km2. They are a primary driver of ecosystem productivity and play a significant role in cycling nutrients, stabilising sediments, improving water quality and carbon storage. They support high species diversity, are critical to sustaining traditional and commercial fisheries, and are an essential food source for the iconic and culturally significant dugong and green turtle. Torres Strait Ailan Kastom is deeply connected to and underpinned by the health of this critical habitat.
Seagrass habitats are ideal indicators for marine health as they are sensitive to environmental change. The natural variability of seagrass meadows can be very high. Occasional or dramatic loss of seagrass meadows has been recorded in Torres Strait over recent decades. Recovery times can range from months to decades, depending on the presence of a viable seedbank, high environmental connectivity and a lessening of drivers causing the declines.
What is already happening?
Information collected by rangers undertaking long-term monitoring programs (over intertidal seagrass meadows) and local Indigenous knowledge is being integrated with recently expanded scientific research and monitoring programs in the region.
Between 2018-2021, dramatic declines in seagrass condition were observed in western Torres Strait. Declines occurred across a range of intertidal reef-top, island and deep-water seagrass communities. Causes being investigated include changes in wind patterns affecting tidal exposure and sediment movement, increased dugong and green turtle feeding density, and seagrass disease. Localised declines were not detected elsewhere, and the condition of seagrass was found to be moderate to good in most areas.
What could happen?
Seagrass condition is affected by changes in environmental conditions (e.g., rainfall, wind, temperature, benthic light, tidal exposure), extreme events (e.g. cyclones, marine heat waves), migratory patterns and abundances of herbivores such as green turtle and dugong, and disease. These factors often interact and are being exacerbated by accelerating changes in climate.
Managing seagrass threats requires a system-level understanding of changes at local, regional, and global levels to ensure that actions are appropriately targeted (e.g., water quality improvement or controlling damaging human activity).
Any large-scale loss of seagrass meadows would have wide- ranging effects in Torres Strait and beyond. Impacts would flow through the ecosystem, affecting species that are dependent on seagrass for habitat, food, and other ecosystem services. It would have far-reaching effects for island communities whose consumption of seafood is among the highest globally and whose Ailan Kastom is inextricably linked to the health of this habitat and the resources it supports.