Threats to sea country

Indigenous management of sea country | Black-striped mussel | Crown-of-thorns starfish |

Many human activities negatively impact on the coastline and marine environment including coral reefs and estuaries. Pressures can arise from local land-based pollution, poor drainage and effluent management, or can result from land disturbance in catchments many hundreds of kilometres away. Some of the issues that need to be addressed in the tropical savannas region include:

• An increase in sediment and nutrient run-off into rivers.
• Developments in the coastal zone including agriculture, building of marinas and expanding industry and housing.
• Loss of inshore habitat such as mangroves and saltmarshes from clearing and development.
• Effects of tourism and destruction of areas of social and cultural importance, and
• The effects of trawling, overfishing and dieback of seagrass.

Other activities related to fisheries and aquaculture, shipping and port industries, and marine tourism and recreation, are all potentially threatening to the health of the savannas’ coastal and marine environments.

Luckily the pressures and problems of urban sprawl, high population density and pollution of rivers and lakes are currently not as extensive in the tropical savannas as they are in other areas of Australia.

However there are some threats which look to impact the tropical savannas coastline considerably. These include the impacts of future sea level rise due to global warming and the changes to coastal ecosystems as they become inundated with salt water. Increases in ocean temperature will also change the way coastal ecosystems function.

Indigenous management of sea country 

• Aboriginal and Torres Strait Islander fishing rights and lack of involvement in management.
• Protection and preservation of sites of cultural significance, in particular Aboriginal and Torres Strait Islander sites of significance.

Black-striped mussel (Mytilopsis sallei)

Introduced marine pest such as the black-striped mussel and crown-of-thorns starfish can potentially devastate marine biodiversity. This mussel is able reproduce at an alarming rate creating monocultures in and around marinas and wharves, excluding other species, fouling the environment and reducing biodiversity. They are spread when they hitch a ride from infested areas on the hulls of commercial and recreational boats. There was an outbreak in several Darwin marinas in 1999, which was successfully eradicated after large scale chemical treatment.

Crown-of-thorns starfish (Acanthaster planci)

Over the past 30 years outbreaks of the coral-eating crown-of-thorns starfish have caused considerable damage to reefs in the Indo-Pacific region, including parts of the Great Barrier Reef. The crown-of-thorns starfish is one of only a few animals which feed on living coral tissue. It gets its name from the dense covering of long sharp spines covering its upper surface. At low densities this animal is just another part of the ecology of a coral reef. However, if the crown-of-thorns starfish population grows dramatically, it can reach densities at which it eats corals faster than they can grow and reproduce. Coral cover can be reduced significantly and result in major disturbance to the whole ecology of a reef. If the number of adult crown-of-thorns starfish in one hectare of the reef rises above about 30, coral cover starts to decline (Great Barrier Marine Park Authority).