City officials are assessing the damage to more than 20 trees at Ala Moana Beach Park.
Vandals put graffiti on the trees and at least two of the vandalized trees are designated "exceptional trees".
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Trees marked as exceptional meet criteria such as rarity or large size, and they are protected by a city ordinance.
"Just a real big lack of respect I think more than anything for the property. Trees are some of the most beautiful things we have here in Hawaii. To seem them defaced like this it's horrible," said runner Kennedy Carlson.
The statewide environmental nonprofit Outdoor Circle says this is the first time it has dealt with graffiti on trees at the park.
Officials are not sure if they can clean the graffiti, but an option is using a wire brush.
Park officials say they have not seen this problem in the past.