Leaders of the G7 pose for a group photo on overlooking the beach at the Carbis Bay Hotel in Carbis Bay, Cornwall. AP

The group of leading economies, holding their first in-person gathering in nearly two years due to the coronavirus pandemic, will agree to protect at least 30 per cent of both land and ocean globally by the end of the decade.

The "Nature Compact" struck to try to halt and reverse biodiversity loss is also set to see them commit to nearly halve their carbon emissions by 2030, relative to 2010.

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It includes mandating the use of only so-called clean coal for power "as soon as possible", ending most government support for the fossil fuel sector overseas and phasing out petrol and diesel cars.

Hailing the pact, British Prime Minister Boris Johnson -- who is hosting the beachside summit in Cornwall, southwest England -- said the G7 wanted to "drive a global Green Industrial Revolution to transform the way we live".

Boris Johnson (right) and Emmanuel Macron confer during a bilateral meeting at the G7 summit in Carbis Bay. AFP

"There is a direct relationship between reducing emissions, restoring nature, creating jobs and ensuring long-term economic growth," he added, in remarks released ahead of the summit's conclusion.

Climate change was a key G7 priority for his government, as it tries to lay the groundwork for hosting the UN COP26 environment summit in Glasgow in November.

But before the pledges had even been formally adopted, environmental campaigners blasted them as lacking enforcement and the necessary scope.

"Despite the green soundbites, Boris Johnson has simply reheated old promises and peppered his plan with hypocrisy, rather than taking real action to tackle the climate and nature emergency," said Greenpeace UK's executive director John Sauven.

He also noted wealthy nations had a "dismal track record" over the last decade honouring international climate finance commitments.

The G7 — Britain, Canada, France, Germany, Italy, Japan and United States — were eager to hold their first physical summit since August 2019 to renew ties after the discord of Donald Trump's four years in power.

Joe Biden has sought to turn the page on his predecessor's international isolationism, seeking to open a new chapter in the Western alliance after Trump alienated and exasperated it at every turn.

Justin Trudeau (right) speaks with Angela Merkel at the G7 Summit in Carbis Bay, Cornwall, England. AP

The UK government turned to its royals to add a dash of grandeur to the G7 detente, with Queen Elizabeth II and her son Prince Charles hosting a Friday night reception with G7 leaders and European Union chiefs also attending.

Joined Saturday by counterparts from Australia, South Africa and South Korea -- with India also taking part remotely -- they then enjoyed an evening beach barbecue around fire pits, featuring a sea shanty band and toasted marshmallows.

Despite the lighter moments, the summit was largely consumed with the tough task of forging a more comprehensive response to the pandemic.

Leaders agreed a declaration to help prevent future pandemics and are expected to commit to donate one billion Covid-19 vaccine doses to poor countries.

However, there they also faced pushback, with critics arguing it provides just a fraction of what is needed to inoculate the world against the virus, which has claimed nearly four million lives globally and is still spawning new variants.