Hawai`i Wildfires: At the Intersection of Climate Change and Biodiversity Loss
By Dr. Alexandra Moore, Senior Education Associate
August 11, 2023
Photograph of wildfire on the island of Maui, at Kupa`a Farms on the west slope of Haleakala volcano, taken by geologist/farmer Dr. Gerry Ross, 8/8/23.
Photo: The endemic honeycreeper `Apapane (Himatione sanguinea) co-evolved with the endemic `Ōhi`a tree (Metrosideros polymorpha). Both species exist nowhere else on Earth. (A. Moore photo).
On August 8-10, 2023, wildfires devastated the Hawaiian Islands, one of the most unique and beautiful places on Earth. These fires come only a few months after many of us lived through the smoke plume from Canadian wildfires, where an unprecedented area of pristine forest has burned this summer. Perhaps you, like me, have been watching with concern as wildfires spread out of control with greater frequency--everywhere from the boreal forests of Canada to the tropical islands of Hawai`i. Reading the news of the fire that raged through Lahaina on the island of Maui, we might wonder how a relatively small brushfire could grow out of control so quickly as to engulf the second-largest town on Maui, without giving residents time to escape?
The answer lies at the intersection of two intertwined environmental crises, climate change and biodiversity loss.
The Hawaiian Islands were first inhabited about 1000 years ago by Polynesian explorers who voyaged from southeast Asia eastward across the Pacific Ocean. Polynesian voyagers carried with them the plants and resources that they would need to survive and thrive on new and unknown islands. Archeologists and paleontologists have documented the Polynesian arrival from the bones and seeds of the chickens, pigs, kukui trees, and other species that they introduced to the islands. These early human inhabitants also took advantage of the native plants and animals that they found in their new home, and they cleared land to plant their staple crops. The same fossil assemblages document the earliest human-caused extinctions of native island species (1).
Photo: Cornell student Kathryn Beaumont holds the fossilized talon of an extinct Hawaiian owl (tentative ID Grallistrix auceps) that she found at Māhā`ulepū Cave, Kaua`i. Length ca. 2 cm (A. Moore photo).
The rates of non-native species introduction and native species extinction increased dramatically with the arrival of European explorers, beginning with British Captain James Cook in 1778. European and American immigrants enthusiastically cleared land for sugar plantations and cattle ranching (and later, pineapple plantations), and introduced non-native plant and animal species from all over the world. Diverse forests were replaced with an agricultural monoculture, and aggressive non-native species gained a foothold. The same fossil sites show a rapid increase in sedimentation rate due to increased erosion from denuded landscapes, as well as the introduction of an entirely new flora and fauna.
Sugar plantations dominated the Hawaiian economy, culture, and native ecosystems for 150 years, leading to the forcible overthrow of the Hawaiian monarchy and the introduction of contract laborers from every country of the Pacific rim and beyond. But by the end of the 20th century the plantation economy of the Hawaiian Islands had collapsed. Cane fields were left fallow and were rapidly overrun by introduced, invasive African pasture grasses. These non-native species evolved in a different and distant ecosystem where they developed tolerance to wildfire. Further, their rapid reproduction rate allows them to overtake the native plant communities that had never faced the aggressive competition that species like guinea grass (Megathyrsus maximus) and fountain grass (Pennisetum setaceum) presented them.
The same time frame marked by the rise of plantations, and expansion of non-native species in Hawai`i, also saw the discovery and development of fossil fuels as the power behind the industrial revolution. Loss of native Hawaiian species diversity and the rise in fossil fuel-produced atmospheric CO2 advanced side-by-side. The resulting change in climate is manifested in Hawai`i as increasingly warm air and water temperatures, coupled with decreasing precipitation across the archipelago.
Figure: Hawai`i Island, satellite image (left) and land cover map (right). Native forest is mapped in greens (wet/mesic forest) and yellows (dryland forest), gray/white is area above treeline, pink is human-cleared former forest (map by Hawaii Forest Industry Association). Native dryland forest is one of the most heavily impacted ecosystems in the archipelago.
Figure: Former dryland forest converted to ranchland, now covered by fire-tolerant invasive pasture grasses on leeward Hawai`i Island (left). Invasive grasses cover more than one million acres statewide. NOAA data (right) showing 70-year record of precipitation (top), air temperature (middle) and temperature projections (bottom) for the Hawaiian Islands (https://statesummaries.ncics.org/chapter/hi/. Photo by A. Moore).
In 2023 most of the Hawaiian Islands are currently in a state of drought, ranging from abnormally dry to severe drought. The high temperatures and low precipitation have left grasslands desiccated and vulnerable to wildfire. In early August the onset of hurricane season sent Category 4 Dora tracking south of Hawai`i, setting up an atmospheric pressure gradient that produced fierce NE winds across the islands. An errant spark exploded through the parched guinea grass upwind of Lahaina.
There is no silver lining to this summer of record-breaking wildfires and there is no consolation to those who have lost lives and livelihoods. But one ray of hope may be this: the same action that will help restore the native ecosystems of the Hawaiian Islands is one that will simultaneously help ameliorate the negative impact of global warming. Forest restoration returns damaged ecosystems to a more healthy state, allowing them to trap and store water within their watersheds, provide habitat for native species, expand diminished biodiversity, shade out fire-tolerant non-native grasses, and sequester atmospheric carbon dioxide as biomass. Storing CO2 in trees removes it from the atmosphere where it would otherwise enhance climate change as a heat-trapping greenhouse gas.
The effort of forest restoration might seem enormous. It is. The resulting drawdown of CO2 might seem small. It is not. Every increment of damage that we can repair is important. It makes the global problem just a little bit smaller and thus a little bit easier to solve. And for communities on the front line, it may make all the difference.
Photo: Cornell University students work with Hawaiian conservation groups to restore the dryland forest ecosystem at Ka`ūpūlehu, Hawai`i Island. In the background are some of the more than 200,000 acres of invasive fountain grass (Pennisetum setaceum) that has overrun the island, encroaching on the Mauna Loa lava flow of 1801 (A. Moore photo).
(1) Burney, D.A. et al., 2001, Fossil evidence for a diverse biota from Kaua'i and its transformation since human arrival: Ecological Monographs, 71(4), p. 615-641.
Author's Note: for those looking to donate to the recovery on Maui, our Hawaiian colleagues have recommended the Hawaiian Community Foundation, www.hawaiicommunityfoundation.org/home