Can’t Cool Down: More than a decade ago at the Hawai‘i Conservation Conference, Stephen Miller of the U.S. Fish and Wildlife Service office in Honolulu expressed his concern about the pace at which nighttime temperatures at high elevations were rising: .441 degrees centigrade per decade at upper elevation forests. “This will have a profound effect on plant and bird species. Most natural vegetation and agriculture crops in non-frost areas are negatively affected by higher nighttime temperatures, due to increased respiration. Increased temperature and stress on natives could favor invasives. Also, warm night temperatures will undoubtedly affect the distribution of malaria in Hawaiian forests and its impact on birds,” he said in his 2008 plenary speech.
Now, according to Susan Cordell of the U.S. Forest Service, who is the science lead for the Hawai‘i Experimental Tropical Forest (HETF) units in Pu‘u Wa‘awa‘a and Laupahoehoe on the Big Island, research suggests that those higher nighttime temperatures are, indeed, harming the trees there. The 50,000-acre HETF was established in 2007 and has a 35-year permit to conduct research and education activities on state land.
In updating the state Board of Land and Natural Resources last month on research in the two forest units, Cordell said the data on nighttime temperatures show “that climate change is affecting our forests.”
“As you increase minimum temperatures, which occur at night or the early morning, trees, which are normally resting during that time, are respiring higher. They’re losing CO2 (carbon dioxide) to the atmosphere rather than keeping it and turning it into sugars for growth. The phenomenon started in Costa Rica,” she said.
Costa Rica has a 30-year data set.
“We have 10 years, but we’re starting to see a similar trend. They saw a strong relationship with tree mortality [and higher nighttime temperatures]. It’s offsetting the carbon balance of the tree. I’m not sure what we can do about it. Documenting and understanding it is important,” she said.
A Bat-Safe Wind Farm? The 21-megawatt Kaheawa Wind Power II wind farm on Maui received Land Board approval last month of a new Habitat Conservation Plan and Incidental Take License that allow the facility to harm or kill more endangered Hawaiian hoary bats (ope‘ape‘a) and geese (nene) than it was originally allowed to in 2012.
In 2014, modeling showed that the wind farm had reached its initial bat take limit of 11. To avoid further take, the facility stopped the turbines from spinning at night unless wind speeds exceeded 5.5 meters per second. The bats are known to prefer foraging at night in low wind. The company reports that it has not had any observed bat take since implementing its low wind speed curtailment program.
Even with zero observed take, there is a possibility some bats were killed and not found. So as of June 30, the facility’s total estimated bat take was 13.
Under the new conservation plan and take license, the wind farm will be allowed to kill up to 38 bats during the license term, which ends in 2032. The allowable nene take would also increase, from 27 to 44.
To mitigate the increased take, the wind farm has already paid nearly $1 million for bat life history and ecology research on Hawai‘i island. It may also fund the acquisition of bat habitat on Maui if take exceeds 30 bats.