Kelp forests are found along 25% of the world’s temperate coastlines in cool to cold, nutrient-rich waters. These forests have some of the highest rates of primary production (biomass) anywhere on Earth. There is a large diversity of kelp species such as those shown in the map below. Kelp forests support high levels of biodiversity, provide valuable habitats and environmental services for coastal communities such as protection from erosion and a source of food.

Global Distribution. Colours and numbers show the distribution of major kelp genera and numbers of kelp species.

Source:Status and Trends for the World's Kelp Forests

Thomas Wernberg, Kira Krumhansl, Karen Filbee-Dexter, Morten F. Pedersen

DOI:10.1016/B978-0-12-805052-1.00003-6. Rightslink licence 5131200204971.

Temperate kelp forests are declining at a global scale.

One study ‘Global patterns of kelp forest change over the past half-century' found that 38% of kelp forests have declined in the past 50 years. In California, giant kelp forests have been replaced by urchin barrens and in Australia, kelp forests of the Great Southern Reef have been lost off the coasts of New South Wales, Victoria, Tasmania and Western Australia.

Overharvesting, pollution, sedimentation, invasive species, heatwaves and the tropicalisation of species are changing kelp forests.

Actions are being taken to halt or reverse this decline and restore kelp forests. These include

• removing or harvesting of invasive species

• creating marine protected areas

• controls on fishing and harvesting species

• pollution control

Different strategies are used in different locations.

Operation Crayweed in NSW is an example of a local response where young kelp was replanted on rock surfaces.

At a global scale, action on climate change is critical to the future of kelp forests.