Pollution / poor water quality, overfishing / overharvesting, sedimentation, invasive species / herbivory, changes to ocean circulations / currents and climate change have been identified as key causes of change to kelp forests. All can be linked to human activities at local, regional and global scales. The cause of change vary between different locations.

The most significant impacts of change have been the loss and degradation of kelp forests, the replacement of kelp forests by algal turfs or urchin barrens and a loss of marine biodiversity. These impacts have economic, environmental and social consequences for kelp forests and the communities that depend on them.

Some consequences of change

Climate change projections and predicted impacts suggest that the kelp forests of the GSR will survive because they are resilient and adaptable, however they face permanent change in their distribution, characteristics and functioning (their environmental processes).

Frequent impacts such as storms, reduce the ability of kelp forests to recover. Further change associated with a warming climate e.g., an increase in storms and warming oceans, will increase the stress on kelp forests beyond which they will not recover. This is known as a tipping point.

Historical data provides a baseline against which change can be mapped. A 50-year global scientific study has shown a large variation in the changes to kelp species and their distribution - with kelp losses in some regions and gains in others.

Studies of kelp forests in northern NSW and Western Australia by universities and research organisations show that the causes and impacts of change on the GSR vary geographically.

Organisations such as the Reef Life Survey Foundation are helping to provide quality, scientific data to record and monitor change. The data can help with management.

Kelp forest ecosystems face multiple threats to their functioning with one change usually identified as a key cause (stressor).

The more frequent the stress events, the greater the impact on kelp.

Carbon emissions from human activities are causing ocean warming, acidification and oxygen loss with some evidence of changes in nutrient cycling and primary production. The warming ocean is affecting marine organisms at multiple trophic levels, impacting fisheries with implications for food production and human communities.

‘The loss of kelp forests is followed by the colonisation of turfs, which contributes to the reduction in habitat complexity, carbon storage and diversity (high confidence). Kelp ecosystems are expected to continue to decline in temperate regions driven by ocean warming and intensification of extreme climate events.’

SOURCE: IPCC: Special Report on The Ocean and Cryosphere in a Changing Climate Ch5 https://www.ipcc.ch/srocc/chapter/chapter-5/