Mauka to Makai: How Maui’s Ocean Life Is Connected
As night falls over the coast of Maui during nesting season, a ʻuaʻu kani (wedge-tailed shearwater) makes their way home. It has spent the day feeding over open water, and now it drops toward land, finds its burrow by instinct, and settles in with the low, haunting moan that gave the bird its name.
Beneath the waves, a honu (Hawaiian green sea turtle) wedges herself under a ledge of coral and sleeps, as a ʻīlioholoikauaua (Hawaiian monk seal) hauls out on the beach to do the same.
Three animals, three habitats, and no obvious link between them. But the Hawaiian people saw the connection long before modern ecology had a word for it.
What Does "Mauka to Makai" Mean?
Mauka means toward the mountain. Makai means toward the sea. Together, these two Hawaiian words describe something larger than direction: a landscape where uplands, shoreline, and ocean work as one living system.
Native Hawaiians organized Maui and the other islands around that understanding. The land was divided into ahupuaʻa districts that typically ran from the high forests down through the valleys, across the coast, and out into the reef. Those who lived within an ahupuaʻa tended every part of it and drew from every part, because they knew what modern ridge-to-reef science confirms: what happens in the uplands shapes everything downstream.
The animals of Maui’s coast are bound by the same connection. Pull on one thread, and the others answer.
How Seabirds Feed the Reef
The shearwater is a creature of two worlds. It nests on land, but its hunger lives far out over open water, where it hunts fish and squid. Other Hawaiian seabirds follow the same pattern. The ʻuaʻu (Hawaiian petrel) nests in burrows high on Haleakalā, while the mōlī (Laysan albatross) and kaʻupu (black-footed albatross) range across the open Pacific.
Every return trip is a delivery. A seabird feeds at sea, carries that nourishment home, and leaves part of it behind as guano, droppings rich in nitrogen and phosphorus. Some of those nutrients find their way back to the water. Around the small islets off Kailua, Oʻahu, where wedge-tailed shearwaters nest in large numbers, researchers found that reefs beside the biggest colonies had more phosphorus in the water, and more of the birds’ nitrogen in their algae, than reefs beside smaller ones.¹
The nutrients didn’t disappear into the open sea. The algae drew them in. This completes a full circle, from the sea to the bird, from the bird to the land, and from the land back to the reef.
What Is a Coral Reef?
People often mistake coral for a bush or a plant. Some look at a reef and see only stone. What they’re really looking at is a city of coral.
Koʻa (coral) is made up of hundreds to millions of tiny animals called polyps. Within those polyps live zooxanthellae, microscopic algae partners that give coral its color and much of its energy. Hard (stony) corals extract calcium and carbonate ions from seawater to build a calcium carbonate skeleton that stacks up over centuries. Like any city, it’s crowded with residents. Fish slip through its narrow streets. Eels and octopus guard their dens. Nearly every surface is alive.
But a city that rich draws competition, and on a reef, one of the competitors is the algae that grows across its surface. A reef overrun by it is in trouble, because algae can crowd coral out or block the sunlight coral needs to survive. On a healthy reef, though, the balance holds: algae fed by seabird nutrients nourishes the grazers that keep it in check.
How Sea Turtles Protect Coral Reefs
Those grazers include one of Hawaiʻi’s most beloved animals, the Honu. They feed mostly on limu, the algae and seaweed that cling to the reef and the rocky shoreline, and with every bite they tip the balance back toward the coral. Reef fish such as lauʻīpala (yellow tang) and manini (convict tang) share the work, grazing algae from the reef’s surface so coral keeps room to grow.
Grazers also return nutrients to the reef. What a honu digests comes back out as waste rich in nitrogen and phosphorus, which helps feed coral and the community around it.² It mirrors what seabirds do: birds deliver nutrients from the land side, and grazers recycle them in the water.
The honuʻea (Hawaiian hawksbill turtle) does a different job. Here, Hawksbills feed heavily on sponges, which can spread across a reef and crowd out coral. By eating them, they clear patches of bare reef where young coral can settle.
A reef kept in balance like this overflows with fish, and that abundance feeds the hunters who depend on it.
Why Hawaiian Monk Seals Need a Healthy Reef
Among those hunters is the Hawaiian monk seal, an endangered species found only in the Hawaiian Islands.
Monk seals hunt on and around the reef, feeding on fish, eels, octopus, and crustaceans, many of which depend on coral for shelter and on healthy reef surfaces for food. A rich reef means a successful hunt. A reef in decline means seals burn more energy searching for prey and gain less from every meal.
But monk seals can’t stay in the water forever. They rely on the shoreline, where they haul out on beaches to rest, molt, and nurse pups. These are critical biological needs that require quiet and space to recover. When seals are disturbed, they may return to the ocean before they are ready.
Why the Mauka to Makai Connection Still Matters
Though the ahupuaʻa is not as prominent today, the connection it describes is as real as ever. It’s easy today to treat each animal as its own issue: a bird problem, a turtle problem, a seal problem. The mauka-to-makai view shows why that falls short. Follow almost any of those problems back far enough and it becomes a people problem, which also means people can be the solution.
The clearest modern example may be rain. The same nutrients that sustain a reef when they arrive naturally, as they do from seabirds, can harm it when they come from human sources. Sewage and fertilizer runoff rich in nitrogen and phosphorus can trigger smothering algae blooms. On Maui, studies have traced nitrogen from wastewater into the algae and coral off West Maui and Kīhei.³'⁴
After heavy rain, stormwater washes across roads, farms, and neighborhoods and carries dirt, trash, pathogens, pesticides, and other pollution downhill toward the shore. The Hawaiʻi Department of Health responds with Brown Water Advisories, warning people to stay out of the water.⁵ For people, it’s a health warning. For the animals that live there, it’s a health emergency.
Several other pressures cross the whole chain as well:
Warming seas. By 2050, 90% of coral reefs are expected to bleach annually.⁶
Marine debris. Fishing line entangles sea turtles and monk seals, and albatross can mistake floating plastic for food and feed it to their chicks.
Disturbance on shore. Crowds can push a resting monk seal back into the water, while pets near burrows can disturb nesting birds.
Artificial light. Fledgling shearwaters leaving their nests at night can be lured off course by bright lights.
Strike one link and the whole chain trembles. That’s why conservation increasingly follows the whole system, from mountain slope to shoreline to reef, instead of one species at a time. It’s the mindset behind our work at The Marine Institute.
How You Can Help Protect Maui’s Marine Life
Protecting Maui’s interconnected ecosystems isn’t about isolated acts; it’s about honoring the connection from mountain to sea. Here's how you can help protect our shared home:
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Sources
American Bird Conservancy. “Fertile Grounds: How Seabird Waste Benefits Land and Sea.” https://abcbirds.org/news/fertile-grounds-how-seabird-waste-benefits-land-and-sea/
Coral Reef Alliance. “The Dynamic Connection Between Sea Turtles and Coral Reefs.” https://coral.org/blog/the-dynamic-connection-between-sea-turtles-and-coral-reefs/
Murray, J., et al. (2019). “Coral Skeleton δ15N as a Tracer of Historic Nutrient Loading to a Coral Reef in Maui, Hawaii.” Scientific Reports. https://www.nature.com/articles/s41598-019-42013-3
Amato, D. W., et al. (2016). “Impact of Submarine Groundwater Discharge on Marine Water Quality and Reef Biota of Maui.” PLoS ONE. https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0165825
Hawaiʻi Department of Health, Clean Water Branch. “Brown Water Advisories.” https://eha-cloud.doh.hawaii.gov/cwb/#!/landing
Reef Resilience Network. “Mass Coral Bleaching.” https://reefresilience.org/managing-climate-threats/mass-bleaching/