Driving emissions down to “net zero” will not be enough on its own to properly combat the climate emergency, the Environment Agency head is warning.

Sir James Bevan is calling on the public and private sectors to adopt “net zero plus” with action to reduce emissions, while adapting to the impacts of climate warming including more extreme weather and rising sea levels.

Adapting to a changing climate is not only necessary but will provide opportunities to build back better from flooding, create greener, cleaner cities and enhance nature at the same time as locking up carbon, he will argue.

The UK has a legal target to cut its greenhouse gases to “net zero” by 2050, which requires cutting emissions as much as possible and taking steps such as planting trees to offset the impact of any remaining pollution.

But even if all the world’s carbon emissions were halted overnight, the impact of pollution that has already occurred would be felt for decades, Sir James, the Environment Agency’s chief executive, will say in a speech to the Westminster and Industry Group Net Zero Roundtable, on Tuesday.

Evoking the Cold War government campaign Protect and Survive, he will say tackling today’s existential threat of the climate emergency could require adopting a variation on the slogan that urges people to “adapt and thrive”.

He will stress the importance of action that simultaneously cuts emissions and helps the country adapt to inevitable warming.

These include measures such as the “keeping rivers cool” project in which the EA and other organisations are planting 300,000 trees along rivers to lock up carbon and keep the waterways shadier and cooler for salmon and trout.

Global average temperatures have already warmed by 1C above pre-industrial levels, with impacts of more frequent and extreme flooding, water shortages, coastal erosion and damage to wildlife and cultural heritage, he will say.

In all future climate scenarios, sea levels will continue to rise, he warns.

He will say: “Even with the ambitious global and national action we all want to see to reduce emissions, some further climate change is now inevitable.

“That is why as a nation we need to be climate ready so that we are resilient to the future hazards and potential shocks that would otherwise impact our economy, our prosperity and our lifestyle.

“In the Cold War, the government ran a campaign called Protect and Survive. If we want to respond to the existential threat we face today – the climate emergency – then we could adopt a variation on that slogan, adapt and thrive.

“We need to design and build our infrastructure, our cities and our economy so that they are resilient to the effects of the changing climate.

“But the point is not just to survive. If we adapt right we can thrive too.”

He will tell companies climate adaptation offers every business a world of new economic opportunities through innovating and driving growth.

But he will add: “The most exciting opportunity of all is the opportunity to create a better world: to build back better when flooding or drought damages homes and businesses; to create cleaner, greener cities which are more beautiful and better to live in than the ones we have now, and enhance nature at the same time as we lock up more carbon.”

National Trust outdoors and natural resources director Patrick Begg said: “The climate crisis is threatening our natural world, eroding heritage and affecting our daily lives.

“There is no silver bullet and we need a strategy that both halts future emissions but crucially also prepares us for what is coming.

“Net zero ambitions are a crucial step but, as Sir James Bevan makes clear, they alone aren’t enough.

“Investment in green jobs; better access to nature and fresher air in towns and cities; projects to restore peatlands that lock up carbon; and an ambitious environment bill with targets for nature’s recovery – these are all crucial for a healthier, more resilient future.”

The National Trust said it was working with communities, partners and Government, and alongside its net zero target, to restore and protect nature and heritage in the face of climate change.