The World Health Organisation (WHO) should declare the climate and nature crisis a health emergency, according to a call to action from health experts across the world.

More than 200 health journals published their warning on Wednesday to create momentum ahead of the next World Health Assembly in 2024. The journals included publications such as The Lancet and The British Medical Journal (BMJ) and also the Medical Journal of Australia.

The editorial appeal says it is a dangerous mistake to consider the climate and nature crises separately.

"The climate crisis and loss of biodiversity both damage human health, and they are interlinked," said BMJ editor-in-chief Kamran Abbasi.

"That's why we must consider them together and declare a global health emergency."

"Health professionals ... have a central role to play in articulating this important message and advocating for politicians to recognise and take urgent action," Abbasi continued.

Climate change contributes to the spread of infectious diseases. Pollution is damaging drinking water sources, and fish for consumption are becoming scarce due to ocean acidification, according to the editorial.

The decline in biodiversity makes it more difficult to feed humanity in a healthy way. More settlement and agricultural construction, as well as encroachment into previously natural areas, are bringing people into closer contact with tens of thousands of species. This increases the danger of diseases or parasites being transmitted to humans, it said.

"Declaring a public health emergency is the highest alert the WHO can issue. It did so, for example, in the case of the coronavirus pandemic. This calls on all member countries to share information and do everything they can to bring the problem under control.

"Declaring a state of emergency does not have any concrete effects. The WHO cannot demand any country implement ways to tackle climate change or other emergencies. It is up to each country to decide."