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Camilo Mora spends his evenings and weekends tinkering with PVC pipes, duct tape and zip ties, working like a modern-day MacGyver to create odd-looking inventions for his greenhouse.

This passion fits in nicely with his day job as an environmental professor at the University of Hawaii. But his best brainstorming takes place not in the classroom, but during hikes with his 12-year-old daughter.

“She’s the one with all the good ideas,” he said with a laugh.

Mora’s greenhouse is currently packed with 11,000 . He hopes to plant all of them in a single day for his .

“Everyone who hears that number for the first time is going to say ‘this guy is crazy what the hell is he talking about,’” he said.

Mora’s “crazy” plan is just one of many to bring greenery to urban Honolulu, restore watersheds and plant millions of trees in Hawaii. These efforts have gained popularity in recent years as individuals and cities look to offset carbon emissions.

“Climate change is a universal problem in the way that it affects the entire world and planting trees is a universal solution because everyone … can understand how it’s good to put a tree in the ground,” said Jean-Francois Bastin, an ecologist studying how forests interact with the global carbon cycle at the .

Bastin said while tree planting may not be the silver bullet some are hoping for, it can be “incredibly” worthwhile in Hawaii because the state’s tropical forests sequester a lot of carbon.

Last year Mora’s team of volunteers planted a record-setting 1,000 trees in an afternoon. Hundreds of volunteers signed up again this year, but the Oct. 26 event was recently postponed after one of the nonprofits pulled out over liability concerns and two landowners changed their mind about accepting trees on their property.

“The bureaucratic process is just insane when it comes to plant trees and unfortunately it got to us,” Mora said via email.

And the clock is ticking: the saplings will outgrow the greenhouse in a few short weeks.

Other Efforts

The City and County of Honolulu is also working on a plan to plant by 2025.

“They’re one of the few pieces of infrastructure that actually accrue benefits over time,” said Matthew Gonser, with .

But city trees are regularly vandalized, stolen and killed.

“It’s sad because someone has actually spent about three to four years caring and nurturing and watering that tree so that it can grow to a certain size,” he said.

Gonser hopes people who plant a tree themselves will have stronger feelings of stewardship, and residents can pick up a free sapling for their yard.

Across all islands, feral goats, cattle, sheep and pigs destroy existing forests and newly planted trees alike, said Emma Yuen, with the Division of Forestry and Wildlife.

Even with challenges from goats and wildfires, the state is 253,000 acres of forest by 2031 and some years the department plants over 100,000 native trees.

“For millennia these forests have been revered as the Wao Akua which is Realm of the Gods,” she said. “It’s very damaging and alarming that so much of these sacred lands have already been lost.”

What’s The Limit?

While many have been watching global tree-planting initiatives with excitement, Bastin, the Crowther Lab researcher, said he realized that no one had actually studied the best place to plant new trees, especially as the climate changes.

“If we’re going to do this we have to do it with purpose,” he said. “We need to know where the best places to plant trees are and not disturb natural systems.”

So, his team of international researchers mapped out where humans 223 million acres of trees.

That new greenery could sequester about 205 billion tons of atmospheric carbon. Bastin said that’s about two-thirds of carbon emitted by humans since the Industrial Revolution, so planting trees isn’t the entire solution.

“All those trees would give us about 20 years … which certainly gives us time to lower emissions,” he said.

MacGyver-ing Our Way Out

While Mora is frustrated that red tape is now postponing his tree-planting event, it’s just the latest challenge.

Last year’s hurdle was to keep the trees alive. About half died after the 2018 planting, which Mora said is far better than the survival rate for wild trees, but this year’s goal is 90%.

Mora rigged up his greenhouse with hand-made fertilizer dispensers and a temperature-regulation system with supplies from a local hardware store.

His most recent invention sits directly outside the greenhouse doors. A brown tarp is stretched over what looks like a hard plastic pot. Until Mora gave the base a firm slap and it jiggled.

“Full of rainwater,” he said before explaining the intricacies of his odd-looking creation.

The tarp is angled so rainwater flows into the bag below. A small device that measures soil moisture is inserted into the ground next to a sapling. When the tree gets too dry, a valve connected to the base of the bag releases some water.

“I knew I had to find a way to make the water last,” he said, because global warming in Hawaii.

If the disputes over liability and location are resolved, volunteers will arm each new sapling with its own watering device. But he’s not completely satisfied with the set-up.

“It uses too much PVC pipe,” he said, noting that it costs about $7 to build. He’s already working on version 2.0, which looks like a giant, inverted mushroom. He can build that one for $5.

“The technology is already out there,” he said, gesturing to the household items used in his greenhouse. “We already went to the moon. This is no harder than going to the moon.”