Ten years ago in these pages, Tom Dinell — widely considered the father of urban planning in Hawaii — warned that Honolulu would face significantly hotter temperatures in the decades ahead. Outdoor life in our island city, he wrote, could become increasingly difficult.
His solution was simple and prescient: Dramatically expand Honolulu’s urban forest.
A decade later, the warning is proving true — and the need for trees has never been clearer.
While Honolulu is making strides, we’re not there yet. The challenge before us is a mindset shift: trees are not a “nice to have” beautification amenity. Trees are “must have” infrastructure.
One step in the right direction has been the city’s recently completed inventory of all municipally owned trees, as should be done for any asset.
Just like roads, sewers, water lines and power grids, trees require planning, investment and regular maintenance. And just as we budget for paving and pipes, we must budget for urban forests — because without trees, our streets and neighborhoods become hotter, less comfortable and less safe.
The city’s Division of Urban Forestry is pursuing a comprehensive strategy rooted in understanding that trees are infrastructure:
Proactive tree management and replacement. For too long, tree care has been reactive — pruning or removing trees only after problems arise.
The city has now completed a comprehensive inventory of its trees, allowing arborists to assess health, lifespan and risk. That means replacements can be planned in advance rather than after failures occur.
Expanding park canopy. Honolulu currently has about 25% urban tree canopy, with a policy goal of 35% by 2035. In passive parks — areas without play fields — that goal should be even higher. Reaching 75% canopy in these spaces would maximize cooling, stormwater capture, biodiversity and public health.
Strategic street planting. Street trees provide shade not only for pedestrians but also for transit users, cyclists, motorists and nearby homes and businesses. To deliver the greatest public benefit, priority for new planting must focus first on major thoroughfares, then secondary roads, and finally neighborhood streets.
Bringing it all together. Understanding trees as infrastructure also means recognizing they require ongoing care, dedicated personnel and reliable funding.
Trees are living systems — they grow, they age, they need pruning, and they respond to heat and drought differently. That’s why the city is planning with tomorrow in mind. We also acknowledge that trees don’t belong everywhere.
The recent Kona-low storms reminded us that trees require proper care and space to grow safely. Healthy root systems, adequate soil and regular maintenance are essential to ensuring trees are assets rather than hazards.
This requires resources, but the return on investment is enormous:
>> Cooler neighborhoods lowers energy bills, encourages walking and benefits everyone, especially kupuna and keiki who are most vulnerable to extreme heat.
>> Reduce stormwater runoff lessens flooding, eases pressure on drainage systems, recharges aquifers and protects nearshore waters.
>> Carbon sequestration contributes to broader climate mitigation goals.
Best of all, trees are infrastructure that appreciate in value! An older, mature tree produces more of these benefits than a younger tree. That’s why care, and preserving the large, sentinel trees we have, is essential.
When Tom Dinell urged Honolulu to plant more trees 10 years ago, he understood that our urban forest would shape the city’s future.
Today we must take the next step: Recognize trees for what they truly are — essential infrastructure for a hotter Oahu.
Building that future will require more than policy. It requires community action. Residents can adopt a street tree, help water park plantings, and support the growth of Honolulu’s urban forest.
The shade we plant today will determine the livability of our island tomorrow.
Roxanne Adams is a certified arborist and administrator of the city Division of Urban Forestry; Daniel Dinell is president of Trees for Honolulu’s Future, a nonprofit founded by his late father, Tom Dinell.
