“Our government must recognise the value of our seas and ensure their protection” André Künzelmann/UFZ

The ocean's riches – such as fish and minerals – make it the seventh strongest economy in the world but its value is plummeting due to over-exploitation and climate change, a report has warned.

The World Wildlife Fund (WWF) report, Reviving The Ocean Economy: The Case For Action – 2015, states the value of key ocean assets is estimated to be around $25tn (£17tn), giving it an annual value of goods and services of $2.5tn – the seventh biggest in comparison to the world's economies and just behind the UK.

The WWF study likens neglecting to ocean's assets "to not investing in a fund that yielded a 10% return".

However, because of climate change and the ways in which industries are exploiting the ocean's products, the value of said goods is quickly deteriorating. It adds that more than two thirds of the ocean's annual value relies on healthy conditions.

WWF-UK CEO David Nussbaum said: "Our oceans are a climate regulator and carbon sink, supporting future global economic growth, as well as providing critical goods and services that underpin the well-being of billions of people. But rising temperatures and increased acidification put all this at risk.

"We should recognise the role our oceans play as an important business asset that requires sustainable management and investment – and governments should fully support and implement the UN sustainable development goal on the ocean."

The report gives three objectives to ensure the sustainability of the ocean: "1) embedding ocean recovery throughout the UN's sustainable development goals, 2) taking global action on climate change and 3) making good on strong commitments to deliver well-managed coastal and marine protected areas."

Lyndsey Dodds, head of UK marine policy at WWF-UK, added: "From a UK perspective, our government must recognise the value of our seas and ensure their protection, starting with swift designation of the next tranche of Marine Conservation Zones.

"These zones – along with other measures - such as improved fisheries management - are essential to safeguard the marine assets that underpin the UK economy".