Hahai nō ka ua i ka ululā‘au.
Rains always follow the forest.¹

Hawaiians carefully studied the topography and geology of the islands for many generations. They saw how volcanic islands grew, and crumbled into the ocean. They were careful observers of climate. They studied the patterns of weather, and gave names to the winds and rains in each valley, plain, and mountain. Intimate knowledge enabled Hawaiian people to forecast the weather, and recognize unusual patterns. They knew when and where rains brought water to the islands. They knew the courses of water traveling across and below the ground. They recorded and transmitted their knowledge through stories called mo‘olelo.

Hawaiian indigenous knowledge can still teach us a lot about the land. The mo‘olelo of Kāmeha‘ikana² describes how Hawaiians used their understanding of weather, ecology and hydrology to develop an abundant community in harmony with the land. Unfortunately, we’ve lost much of the detailed Hawaiian knowledge that surveyed every corner of the Islands. The knowledge faded away when we lost the people who kept the mo‘olelo alive.

Modern science has been able to reveal some of the same empirical knowledge once gathered by generations of  Hawaiians watching over the land. What has been missing from modern science is the personal connection between people and the land.

We have a personal interest in supporting all life on Earth. Our journey to the Moon gave us the perspective to begin realizing that were all living together on a tiny speck in space. Science and engineering is slowly guiding us back around to the indigenous point of view that the fate of all life on Earth is interconnected. If we carefully connect the moral lessons in mo‘olelo to scientific study, we can begin to unlock the detailed indigenous knowledge that allowed the Hawaiians to create an ‘āina momona, a bountiful land.

Ola i ka wai

“Ola i ka wai” means “water is life.” Hawaiians realized that an island ecosystem is fragile and can easily be thrown out of balance if water is not managed correctly. They recognized that the mountains and the sea are connected by the flow of water. Actions in one place can affect the whole system.

The flow of water in the Hawaiian Islands begin in the air above the ocean. The warm ocean evaporates filling the air with moisture. The Pacific Trade Winds steadily blow from the northeast for most of the year. The northeastern side of an island facing the trade wind is is called the windward side. The opposite southwestern side is called the leeward side. The leeward side is sheltered from the wind by the central mountains of each island, and is generally drier than the windward side.

The trade winds generate the majority of fresh water for the Hawaiian Islands. When the trade wind encounters an island, the warm moist air from over the ocean is pushed up the windward side of the central mountains. The air cools as it rises, and forms clouds. The clouds release their moisture as rain on the windward mountain slopes. The air that continues over and around the mountains to the leeward side is drier and less likely to produce rain. 

 Some islands like Lāna‘i, are relatively dry because larger islands block the trade winds. Maui shields Lāna‘i and Kaho‘olawe from the trade winds. Small Islands like Ni‘ihau and Kaho‘olawe are even drier because their mountains aren’t high enough to produce rain from moist ocean air.

A second source of rain for larger islands is a convectional climate. A convectional climate is created when heated air over hot dry coastal land rises up into the mountains. Cooler moist ocean air is drawn inland by the convection currents, and pulled up the mountain where it cools and releases rain. These convectional climates can produce rain on the drier leeward sides by drawing in fresh moist ocean air.

Ecological Zones

The Hawaiian Islands can be divided into different climate and ecological zones. The climate zones describe temperature and weather of a large area, and the ecological zone describes what kind of life lives there. These zones are largely determined by average rainfall and temperature. Whether a place is on the windward or leeward side of an island can affect the rainfall. Elevation determines the average temperature, and it can affect the rainfall too.

The average temperature cools the higher up you go. The average temperature of Hawai’i at sea level is about 30º Celsius (85º Fahrenheit). At the peak of Maunakea, the tallest mountain of Hawai’i, the average temperature is near freezing, 0º C (32º F). Different elevations have different ecological zones.

The highest mountain peaks of Hawai‘i and Maui are in the alpine zone. These areas are above the clouds and are very dry. The sun is very intense during the day, and temperatures often drop to freezing at night. Very few plants or animals can survive in the alpine zone.

The subalpine zone is below the alpine zone. More plants are able to grow in this zone, but it’s still cold and dry.

The montane zone is in the middle elevations. Clouds form here, over cool wet rainforests. Toward the edges of the rainforests are mesic forests that receive moderate rainfall. The mesic forests have the most native plant and animal diversity.

The forests in the montane zones are critical to the health of the island ecosystem. Healthy rainforests provide abundant fresh water for the rest of the island. Forests create cool spots in the mountains where clouds form and trees can capture the mist, fog and rain. Vegetation holds a thick layer of topsoil in place with roots. This vegetation and topsoil also soften the impact of rain on the ground. Water is allowed to slowly absorb deep into the ground, where it can recharge the underground aquifers.

The interior of the Hawaiian Islands store water in cracks and fissures in the rocks, deep in the mountains where magma once flowed up the center of ancient volcanoes. When the volcanoes became inactive, the magma cooled and solidified in vertical impermeable rock walls, or dikes, that go miles deep. These structures contain water and hold it like giant underground water tanks.

The fresh water slowly works its way down through the interior of the islands. When fresh water percolates down closer to sea level, it forms a lens of fresh water that floats on top of the more dense salty ocean water.

The land that channels rainfall into streams and rivers is called a watershed. Rainwater has difficulty penetrating the ground without forests. Rainfall on watersheds without forests washes the topsoil away directly into the ocean, where it smothers the sea life with silt. The islands are less habitable without healthy forests covering the watersheds.

Below the montane zone is the lowland zone. The lowland is a diverse mix of microclimates. There are very dry desert areas, dry forests, and warm wet rainforests in this zone. The windward sides are usually wetter than the leeward facing regions.

Below the lowland zone is the coastal zone. Windward coastal zones can be hot and wet. The leeward coastal zones generally receives very little rain and can have arid climates. 

The Hawaiian Islands have two seasons, dry and wet.³ The dry season, called Kau, is April through October. The dry season weather is dominated by consistent trade winds. The wet season called Ho‘oilo is November through March. The trade winds become less stable in the wet season, and rain can come from different directions.

Because of the complex interaction of wind and island topography, some areas are dry in the winter, and wet in the summer. Different weather patterns moving across, and between, islands result in a complex patchwork of varied ecological zones. There are more ecological zones in the Hawaiian Islands than any other place of comparable size. The Hawaiian ecosystems have developed over millions of years to create a balanced environment that supported life from the mountain peaks to the seashore.

The akua describe the functions of nature.

Hawaiian religion and mythology is a library of environmental knowledge, developed through careful observation of the land for many generations. The attributes and relationships between the gods describe the functions of nature. For example, the water cycle is embodied in the akua Kāne and Kanaloa.

Kāne is the god of the sun and surface fresh water, and Kanaloa is the god of underground water and the ocean. The relationship of the two brothers together describes the water cycle. The sun of Kāne heats the ocean to form clouds which rain fresh water onto the mountains. The waters of Kāne flow into the ground and refill the underground aquifers of Kanaloa. The subterranean waters of Kanaloa flow underground and emerge as springs which feed streams that flow to the ocean, thus completing the cycle.

Artesian springs, where groundwater comes to the surface are said to be the work of both Kāne and Kanaloa working together. Kanaloa would point out the source of underground water, and Kāne would pierce the ground to allow the water to come to the surface.

Hawaiian religion considers the functioning of natural cycles to be the living manifestation of the gods. Natural phenomenon are sacred. Devout practitioners strive to align human activity with nature.

Ahupuaʻa

Traditional Hawaiian land management helps keep the land abundant by enhancing the effectiveness of natural functions. Hawaiians developed the ahupua‘a, a traditional land division that considers the entire watershed from the mountains to the sea as a single unit. Each ahupua‘a was a self sustaining ecosystem managed by a konohiki. The konohiki carefully coordinated the use of water on the land, and fishing in the sea.⁴

In the ahupua‘a, water was generated in the mountains by forests capturing clouds and rain. Most of the upland watershed was reserved for wildlife, and considered the sacred home of the akua. From the top of the mountains through the forests was considered wao akua, the realm of the gods. Hawaiians protected these lands and maintained them in their natural state. It was the source of water for the land below, the wao kanaka, the realm of humans.

Rivers flowing down from the wao akua into the wao kanaka were distributed into flooded taro fields. Adjacent fishponds stored more water, and provided habitat for fish, and birds. Nutrient rich fresh water from the fields and ponds continued to flow down to the ocean into brackish water fish ponds along the coast. The ocean fishponds were a place to farm seaweed, and provided young fish a safe habitat to grow. Fishing grounds further offshore were also managed by the konohiki of the ahupua‘a. Food was provided for the people of the ahupua‘a while also enhancing the abundance of all life in it.

Water was distributed and stored throughout the watershed to keep the land consistently irrigated, and provide the oceans with a steady flow of nutrients. The rain and water flowed abundantly when the upland was full of forest trees, and the lowland was irrigated by flooded taro fields, and fish ponds.

The stories of the gods educated people to manage the land in a way that enhanced the natural ecology. Hawaiians worked to create a self sustaining system that grew because they put in more than they took out.

Human activity in modern times

Starting around the 1800s the traditional Hawaiian system of land management began to change. The ‘āina was converted into a resource to be exploited for immediate profit. People  wanted to take out as much as they could from the land with minimum input. Large scale changes were made for short term gains. These changes quickly turned into long term problems that we’re still dealing with two hundred years later.

 Forests were cleared to make room for livestock ranching and plantations. Water was diverted from its natural course to irrigate plantation land. These modifications to the land cause the drier leeward sides to have less ability to hold water, and takes water away from the wetter windward areas. In the 21^st century, much of the former sugarcane and pineapple plantation land has been abandoned, left to be overgrown with invasive grasses. Invasive plants combined with chronic drought has lead to catastrophic wildfires.

Wetlands and flooded kalo fields were drained and developed. The reduction in vegetation and loss of natural reservoirs amplifies the effects of runoff from urban areas. The Islands become chronically dry and are more susceptible to flooding.

Modern use of the land has had the opposite effect of the ahupua‘a land management system. Water is diverted and wasted without regard for the health of the interconnected system of life on the land.

For example, Lāhainā, on Maui, is a very hot dry place that experiences frequent droughts in modern times. Before the 1800s it used to be called the “Venice of the Pacific.” Hawaiians recognized that the natural flow of water down from the mountains created a lush wetland near the coast. They enhanced the extensive wetland and built canals to irrigate crops and create large fishponds. This was the royal home of Kaulahea who famously planted a magnificent grove of breadfruit trees there. His kolohe son Kaulula‘au was also famous for uprooting some of those trees.⁵

Starting in the 1800s, water was incrementally diverted to irrigate sugarcane plantations in west Maui. Even after the sugarcane industry had abandoned the area, the water was not returned to its natural course. Drought and abandoned sugarcane fields full of invasive grasses contributed to a disastrous wildfire that totally destroyed the town in 2023.

The value of studying Hawaiian culture is in their relationship with the land. Indigenous culture makes the welfare off all life on the land a personal obligation. Indigenous cultures recognize that we are part of our environment and have an obligation to support it.

Water is life. When water is managed to sustain the natural land, nature will create water to sustain us all. We already have all of the knowledge and ability to bring the ‘āina to a state of abundance. What we are missing is the collective commitment to live in harmony with the land.