In 1913 the botanist and explorer Joseph Rock wrote of the striking flora of the dryland regions of Kaʻūpūlehu, Puʻu Waʻawaʻa and other leeward regions — where he found the richest tree growth of his botanical surveys.
“It is in these peculiar regions that the botanical collector will find more in one day collecting than in a week or two in a wet region… not less than 60 per cent of all the species of indigenous trees growing in these islands can be found and are peculiar to the dry regions or lava fields of the lower forest zone.”
The difference between the dry forests of today and those of 1913 is staggering. Less than a hundred years later, 90 to 95 percent of dry forest had disappeared, and more than 25 percent of the species of these ecosystems are on the federal endangered species list. Instead of expanses of dryland habitat there are scattered remnants, and the surviving plants, animals and insects cling to a precarious existence. Hawaiian dry forests have followed the fate of tropical dry forests globally.
For native people of the region these plants and lands were considered family, or ʻohana. The ancient Kumulipo creation chant reveals a complex relationship and dynamic continuum between people and the things of the skies, land and ocean. Within the Kumulipo, plants of the uplands have ocean counterparts — the dryland alaheʻe (walaheʻe), wiliwili, ʻūlei, piko and kauila (uwila), and the maile seedling (kuhonua).
The kapu system, the ancient Hawaiian management of scarce resources, is no longer in place. The thinking behind it is still valued: that the highest relationship with these rare kupuna trees is the spiritual guidance and comfort of their living presence, and that we should mālama them as we would any beloved elder.
Take care of the land and the land will take care of you.
Dry forests receive less than 50 inches of rainfall a year and sit most often on Hawaiʻi’s dry leeward coasts through to mid elevations. They are uniquely diverse: on Hawaiʻi Island they are also found in Puna and Kaʻū, and at high elevation in the palila habitat and māmane forests of Mauna Kea. Native plants, insects and birds once lived in prolific dry forests, thriving in a dynamic, richly biodiverse environment.
More than 100 native plant species, including the endangered kauila, uhiuhi, kokiʻo, ʻaiea and halapepe trees. More than 25 percent of Hawaiʻi’s endangered plant species are found in dry forests. Birds such as ʻamakihi and the rare palila — an endangered honeycreeper — live in dry woodlands. The ʻalalā, the Hawaiian crow and a key dry forest seed disperser, has been the subject of repeated reintroduction attempts. The endangered ʻōkaʻi, or Blackburn’s sphinx moth, also makes its home in this habitat.
Land development and deforestation, wildfires, invasive species — plants, animals, insects and fungal diseases — grazing by ungulates such as goats, sheep and cattle, and seed predation by rodents have all contributed to degradation and fragmentation. About ninety-five percent of these forests have been destroyed, and many experts estimate that less than three percent of the remaining habitat can be considered healthy.
Restoration is labour-intensive. It usually begins with fencing to keep out grazing ungulates. Invasive species such as fountain grass and woody species are then removed, and native species planted and often irrigated until they take hold. As the system recovers and begins to self-regenerate, maintenance eases. Firebreaks, rodent control and fence maintenance remain critical. Techniques keep improving, but dry forest still demands a great deal of care.
Fountain grass (Pennisetum setaceum), an introduced ornamental now common through the drier leeward areas of Hawaiʻi Island. It suppresses native vegetation and fuels the fast, dangerous wildfires that are devastating to native ecosystems. Maintaining firebreaks matters to restoration and to everyone living nearby.
Dry forests hold species of rich biological and genetic importance found nowhere else on the planet. Like rain forests they help capture rain to replenish aquifers, and they absorb and store carbon. Given probable warming, conserving dry forest species already adapted to heat and drought could matter well beyond Hawaiʻi.
These public and private lands hold remnant dry forest and represent a remarkable diversity of historical, natural, cultural and scientific resources. Other islands have their own efforts — the Auwahi project on Maui, and work in the Waiʻanae Mountains of Oʻahu.