KOOLAU MOUNTAINS (KHNL) - It takes 25 years to produce just one glass of drinking water.
The Koolau Mountain's watershed, that forms Oahu's windward coast, produces the majority of the drinking water on the island.
In this Earth and Sea Project report, KHNL follow a partnership involved with preserving the delicate plant balance in Hawaii's native forests.
This is what a healthy forest looks like.
"You look at our native forest and you'll see many different types of species co-existing together to create a multi-canopied diverse ecosystem," said Miranda Smith, a Watershed Partnership coordinator.
Miranda Smith takes an active role in maintaining a healthy balance between indigenous and invasive plants.
"We're just continuing the belief that by protecting the forest we are protecting our drinking water and other resources that are associated with that," said Smith. "Water here on Oahu travels less than 23 miles from where it falls to our homes, so really the land in our backyard affects the drinking water that is available to us."
In an aerial tour from Chopper 8, we see a forest taken over by invasive albizia trees.
"When you look at invasive species in the summit areas you'll see a large blanket of one type of species, one canopy level," Smith said. "If you take a closer look you don't see the diversity that you would normally see in a native forest in Hawaii or anywhere else really. We're walking through a large patch of strawberry guava you look to our left, look to our right you can see nothing else."
That's why the Koolau Mountains Watershed Partnership was formed. Landowners work with water managers to protect and maintain healthy native Hawaiian forests.
Healthy forests produce a sustainable water source for generations to come.
"The rains always follow the forest and there are islands and certain ecosystems that are no longer forests and the rain doesn't fall there anymore."
When albezia and strawberry guava take over the native forests, it becomes a battle for light, nutrients, and space.
Native plants are no match for invasive species.
"You see that yellowish patchy almost grassy area right there?" asked Smith. "If there's a disease event it can wipe out acres and acres of forest just because there isn't the diversity and that robustness there that an ecosystem needs to be sustainable."
Miranda and her team search out invasive species with the permission of landowners to remove them.