“The Island of Hawai‘i as a Model for Understanding How the World Works”
Prof. Peter Vitousek, Population and Resource Studies, Stanford University
View the accompanying PowerPoint presentation (9.5 MB).
I was born on Oʻahu and I graduated from Hawaiʻi Preparatory Academy here on Hawaiʻi Island. For the past couple of decades, I’ve spent about 3 months a year on this island conducting research.
What I have learned from my work is that Hawaiʻi Island is a model system for understanding life, land, and culture. What we learn from the complex, populous society that was here before us can help to illuminate our understanding of this place, as well as the world’s understanding of evolution, ecosystems, and human societies.
In scientific fields like molecular biology, we typically study model systems as a means of understanding broader truths. In selecting model systems, we look for an ideal compromise between complexity and tractability. Similarly, in selecting a model for studying evolution, the Hawaiian Islands are an ideal choice because it is a complex archipelago, but not so large that we can’t still understand it.
In the Galapagos Islands, Charles Darwin could identify differences between species on different islands, but his findings pale in comparison to the radiation of species which occurred on Hawaiʻi Island. For example, Hawaiian honey creepers evolved from a single common ancestor into a spectacular variety of species. A single ancestor adapted to inhabit a great range of different environments here, and, as a result, many combinations of traits evolved. Even though we have lost many of these species, there is so much to learn from the variety of species that still exist here.
When we study ecosystems, we consider the dynamics of the whole system, including both its structure and its function. Hawaiʻi Island offers relative simplicity in terms of the whole system. The island has a consistent basalt volcanic bedrock and topography; and it is situated in the most isolated archipelago on Earth. This means that there were relatively few ancestral species which adapted to inhabit different climates along a continuous gradient, ranging from Hāpuna Beach which receives just 7 inches of rainfall annually to the summit of Kohala Mountain, which receives 180 inches of rainfall annually. There is tremendous variation among the species which evolved here on this same rock. There is no better place on the planet to study how climate affects species and ecosystems than here on Hawaiʻi Island.
This fact makes Hawaiʻi Island a tremendously important resource in terms of global climate research. The measurements of rising carbon dioxide levels taken on Mauna Loa provide one of the clearest indications that humans aren’t living sustainably on the planet. By studying the lava flows on this island, we can understand how climate shapes ecosystems: as it gets warmer, we can see what the consequences of this warming are. What we see is that the rate of decomposition outpaces the rate of production. What this means is that when the temperature rises, it’s possible that ecosystems will feed back to reinforce that change. We can see this just by analyzing different lava flows on the island which are exposed to different temperatures.
There is also a distinctive rock chemistry here, something which is special and exciting to geochemistry nerds like me. We can use geochemical tracers to track nutrients in our ecosystems, because they come from a distinct underground source (lava). We know that soils change over time as they age. As nutrients present in the original rock are used up, plants rely on nutrients which come from rainfall. Most nutrients in wet forests here were depleted from the soil within 10s of thousands of years, except for phosphorus which takes much longer to become depleted. What this means is that nutrients to feed Hawaiʻi’s forests are arriving here from somewhere else. We have found that the most important source of phosphorus for ancient soils on the Island of Kaua‘i is dust blown here from the Gobi Desert in Asia. The fact is that dust from Asia is feeding our older forests.
If we ask where else in the world this is happening, we see that all of the world’s rainforests depend on dust blown over thousands of miles from other places. For example, the Amazon Rainforest is dependent on Sahara Desert dust for its nutrients, and so on. These wind delivered nutrients are vital to supporting the world’s forests. Our findings here led to this remarkable discovery. The unique features of the land here on Hawaiʻi Island make it particularly valuable for enhancing our understanding of global environmental phenomena.
Hawaiʻi Island is also a model for understanding cultural evolution. Many of the diverse societies that inhabit the Pacific Islands have common origins because the Polynesian people settled these various places. The Polynesians sailed on deliberate voyages of colonization and exploration, so the same original society settled on lands that were very different. Over time their societies adapted to the unique conditions of their islands, to enable the people to live more efficiently in each place. When the land here shaped their cultural traditions, the Polynesians became Hawaiians.
Hawaiian agriculture is an excellent example of how the people who settled Hawaiʻi Island learned how to farm lands that most continental people could not have survived on. The Hawaiian people intensified agricultural production on this island through multiple pathways, and they sustained their productivity for centuries on very rugged lands. The Hawaiian people were prodigious farmers. They developed irrigated wetland systems on the windward side of the island, as well as rain fed dryland systems on the leeward side of the island.
The wetland systems of Kohala and Waipiʻo have been sustained to the present day, even through massive cultural disruptions over the past two centuries. Their dryland systems are not nearly as well known. Remnants of these dryland field systems cover about 25 square miles of land in windward Kohala. These field systems were abandoned when the Hawaiian population was devastated by introduced diseases. About 90% of the entire population died, and the survivors either moved to larger towns or to farm the wetlands.
The rain fed dryland field systems required much more labor than the wetland systems and were not as productive. They were probably more vulnerable to climate change and environmental change than the wetland irrigated systems were. We still don’t have a clear understanding of the system of walls and paved trails that ran extensively along the dryland farmed areas. These dryland systems are found only in a few places on the younger islands, while irrigated wetland systems were dominant on the older Hawaiian islands. Of the systems on Hawaiʻi Island, we think that about 97% of them were dryland systems and 3% were irrigated systems. These rain fed systems are a Hawaiian invention, and they are part of our legacy here. Such systems are not found across Polynesia: the intensity of cultivation that evolved here depended on a great culture to produce and sustain production on marginal lands – lands that we are not doing much with now. We must recognize that the Hawaiians were not a group of people who simply planted gardens in the forest; they produced surpluses that drove the expansion of their society and sustained them through generations.
We must also acknowledge the extraordinary scale of the society that preceded us on this island. We think that it might have taken 165,000 people to farm the field systems of Hawai‘i and Maui, so the total population was much greater, perhaps 500,000 people – not counting those fed primarily by wetland systems. While these calculations, like all estimates of pre-contact populaton, are challenging, it’s clear that there were many more people living on this island 250 years ago than there are today, and their population remained large for many years.
It is indisputable that this population sustained itself for centuries. These islands were their world: the Hawaiians weren’t importing anything and their energy source was their muscles. We must, therefore, pay serious, humble, and insistent attention to that society – how they worked and how they lived. The fact is that they worked a hell of a lot harder than any of us would like to work. Can we learn from how they lived and how they thought about living in the long term on an island? Certainly we can. The Hawaiians should serve as a model for us as we look for ways to live sustainably on this land.
The Hawaiians definitely knew where to grow their crops. They knew where the sweet spots in the soils were – where the rocks were still able to supply some of the nutrients their crops needed to thrive. Given what I understand of what the Hawaiians knew about farming, I am sure that they knew some things that we haven’t discovered yet. They sustained a high level of productivity and a large population for generations. We are still working to discover what they knew about agricultural cultivation that we don’t know today.
The greatness of the land, the greatness of the life on the land, and the greatness of the culture that developed here are the kind of greatness that appeals to scientists. The measurable results that were achieved here on Hawaiʻi Island are greater than what we are achieving today.
Whatever we do here, we’ve got to achieve that level of greatness in our work. We need to generate measurable results to restore the greatness of the land, the greatness of the life on the land, and the greatness of human culture.