Hundreds of thousands of mussels have been cooked to death on a beach in New Zealand’s North Island, with experts saying more will die as the effects of the climate crisis accelerate.

The mass die-off in Northland was sparked by “an exceptional period of warm weather” combined with low tides in the middle of the day, which had exposed the shellfish, said Dr Andrew Jeffs, a marine scientist from the University of Auckland.

He said more marine life would soon be affected by climate change, and there was little that that could be done to protect the vulnerable shellfish, other than manual protection measures such as shadecloth, which were impractical and “unrealistic”.

Northland is experiencing drought conditions, with many parts of the region not seeing rain for a record-breaking 40 plus days. The effects of the drought have been severe, with Kiwi birds perishing as they search for water, and tankers of freshwater urgently trucked in to fill rainwater tanks in remote communities.

Exposed at a time of day when the sun was at its most intense, hundreds of beds of mussels had been “cooked” by the sun, Jeffs said.

Scientists had observed mussels suffering under changing weather conditions for a decade, but conditions were now getting more intense and devastating for the animals. “I think we’re going to see entire communities of marine creatures change,” said Jeffs.

“These tidal areas are already a very intense place to live and have got very hot sunshine during the summer, it only makes it more intensive. It will only be the very toughest plants and animals that will survive there.”

According to local Northland resident Brandon Ferguson, the smell of the dead mussels was pungent and disturbing.

“It smelt like death and most of the shells had already been cleaned out by gulls and other sea life, but there were still hundreds of full mussels, dying mussels and dead mussels washing in and some just floating around in the tide,” Ferguson told the Northern Advocate newspaper.

“It was heartbreaking to see. Some were still washing in, but not knowing what was wrong, we didn’t touch them, there were more than 500,000 empty shells that we saw.”

The Ministry for Primary Industries said it was investigating the mass die-off and urged people not to collect or eat the affected mussels.

Jeffs said mussels were ecologically very important for New Zealand’s coastal environment, but it was likely they would disappear from reef areas, as conditions became increasingly adverse, especially during summer.

“This is large-scale, whole reef systems being dried out and dying,” Jeffs said. “We’re just going to lose them”