The royals continue their tour of New Zealand with a walk around Auckland's Viaduct this afternoon.
Earlier, the Duke and Duchess of Sussex tossed gumboots with school children at their first official engagement in Auckland.
Prince Harry and his wife Meghan, who married in May, were at the North Shore Riding Club this morning to dedicate a 20ha section of native bush to The Queen's Commonwealth Canopy; a conservation initiative by Commonwealth Nations launched in 2015 to mark the Queen's long service to the Commonwealth.
The couple, who are expecting their first child in the Northern Hemisphere's spring, are in New Zealand as part of their first tour of the South Pacific.
Their Royal Highnesses were welcomed to the riding club, and to Auckland, with a pōwhiri and mihi by local kaumātua, as hosts scrambled to shelter them with umbrellas during a rain shower.
The duchess was dressed all in dark colours, including black J Crew jeans and a Karen Walker blazer.
About 100 members of the QEII National Trust, which oversees the QCC in New Zealand, and children from nearby Pinehill School attended the private dedication ceremony.
Prince Harry said he and Meghan were delighted to open the covenant.
"For those of you who do not know, The Queen's Commonwealth Canopy – or QCC - is a unique network of forest conservation projects."
The QCC aims to help protect native forests.
The duke said the QCC was a cause close to both his and his grandmother's hearts. New Zealand had been one of the first countries to join the initiative and since then had registered more than four-and-a-half-thousand covenants.
"When you think that each of those covenants is enabling the protection of important areas of biodiversity on private land - that is a huge achievement and one that deserves recognition.
"And as I learned in the car, there are no incentives. Farmers are doing this because it's the right thing to do."
Pinehill School pupils sang waiata for the royal couple and helped the duke and duchess plant native trees.
Meghan planted a kōwhai tree, a nod to the kōwhai flower motif included on her wedding veil.
Prince Harry planted a pūriri, which is indigenous to the northern North Island.
The duchess could be heard praising the children for their help. "Well done," she said.
Alex Chatterton, 11, planted a tree with the Duchess. He said she asked him why he wanted to plant the tree and said, "let's get started" and offered him gloves.
He described the royal pair as "nice, caring".
The royal couple's competitive streak came to light as they joined the children for a gumboot throwing contest.
Meghan's team beat Prince Harry's after the duchess lobbed her boot about a metre farther than her husband.
Ryen Anderson, 10, was on Meghan's team. She said Prince Harry told the group he would win next time the couple competed in the sport.
Isabella Iti said their Royal Highnesses "looked like they were really trying to throw the gumboot as far as they could".
"There wasn't too much of a rivalry. I think she was thinking that there was no chance that she would win. But she did."
Meeting the Duchess was "awesome".
"It was amazing," the 10-year-old said.
QEII Trust chair James Guild presented the duke and duchess presented with several gifts from the trust and community, including a pair of green baby-sized gumboots emblazoned with kiwi, a baby shawl and two pounamu.