Letters

‘Ohi’a Canopy Dieback A Natural Process

The recent proposal to exclude 4,000 acres from the Pu’u Maka’ala Natural Area Reserve is not a good idea. The disputed area was subjected to severe ‘ohi’a lehua canopy dieback during the 1960s and early 1970s, and yes, it is now heavily infested by palm grass and other alien species.

Intensive research during the 1970s and 1980s clarified that this canopy dieback is not a disease (as formerly assumed) but a recurring natural process in aging ‘ohi’a forests. We found that the Hawaiian montane rainforest forms a spatial mosaic of forest stands or forest segments that belong to different generations. Older forest segments and those under soil moisture and nutrient stress can lose their canopy during periods of severe weather and are thereafter unable to recuperate, while younger, more vigorous stands regain their full foliage.

At the same time, canopy loss of the declining ‘ohi’a forests triggers the reproduction of a new generation of ‘ohi’a trees. However, this new tree generation can only develop if there are sufficient “safe sites.” Such safe sites for ‘ohi’a regeneration are tree fern trunks and old, moss-covered logs, provided these substrates are not totally hidden under alien plants.

Dieback stands are particularly sensitive to invaders; at the same time, dieback stands are the sites of forest rejuvenation.

In the 1985 book, Hawaii’s Terrestrial Ecosystems – Preservation and Management, I wrote, “It is not sufficient to search for good and healthy looking mature ‘ohi’a forests – and to set these aside believing they will remain healthy looking and good stand examples forever. In the next 50 or 100 years those good-looking, closed-canopy forests may undergo dieback” (p.41). Dr. Jim Jacobi has informed me that part of the good-looking Pu’u Maka’ala forest has already undergone new dieback since 1985.

Thanks for exposing the dilemma with the state’s Natural Area Reserve System. Certainly, employing Kulani inmates in Natural Area management would not “bust” the state’s budget. Instead, their employment would make good use of our tax dollars. Moreover, it would be a boost to the morale of Kulani inmates if they were properly informed of the valuable community service they could per–form.

Professor Dieter Mueller-Dombois

Department of Botany University of Hawai’i, Honolulu

Alternatives to Eradication

In the November 1999 issue of Environment Hawai`i, you seem to have come down heavily in favor of two assumptions:

1. Feral animal populations (deer, pigs, goats, etc.) are out of control in Hawai’i, are threatening indigenous species, have no inherent right to live, and hence must be eradicated.

2. The only possible means of eradication are lethal.

I would probably not argue strongly against most of assumption one. However, assumption two is debatable. It is surprising that your publication did not touch, at least briefly, on various contraceptive technologies that control species populations.

For instance, our own species relies widely on birth control pills, usually sterol hormones. In controlling a feral animal population, sterol contraceptive agents would be a poor choice since they are absorbed undigested and hence would move up the food chain into human hunters. Additionally, they induce side effects and behavioral changes in their feral targets.

A more agreeable approach is the contraceptive vaccine. There are a number of variants, but the general idea is the same. A protein or glycoprotein vaccine is introduced into the target animal, usually by darting, and the animal’s immune system generates antibodies against the vaccine antigen that cross-react against some essential reproductive glycoprotein, usually in the zona pellucidda (ZP) surrounding the ovum. This blocks sperm receptor sites on the ZP and halts the reproductive process prior to conception. These have fewer systemic side effects and are also digestible, so they do not move up the food chain. The disadvantage here is that darting is as time consuming as hunting and snaring.

Various alternate strategies are being developed. Australians, plagued by rabbits, have spliced a porcine ZP glycoprotein into a virus that causes a non-lethal infection in rabbits. The rabbits then pass this contraceptive “cold” around to all their rabbit friends. No one gets killed, the process is spread by a contagious virus, and there are no side effects – except, perhaps, for a few disgruntled rabbit mothers wondering where all the babies went. For details, please search on the abbreviation “PZP” or go to the following web sites:

salonmagazine.com/news/1997/12/22news.html (deer)

biology.usgs.gov/cro/98blm-5.htm

The contraceptive vaccine technology is still in development and may require another 5-10 years to be practical in Hawai’i. However, from the tenor of your article, few people here seem to even be aware of it. Surely anyone concerned with the control of wild and domestic animal overpopulation should be informed about the vaccine and be prepared to assist politically with its introduction.

Doubtless animal populations must be controlled, but trying to do it with guns, poisons, snares, and trapping is like trying to empty the ocean with a teaspoon.

William Harris, M.D. Honolulu

Betrayed!

The November issue of Environment Hawai`i is a grave disappointment. It is writing that further divides people (often already splintered) concerned about environmental issues.

In your pages, you propose eradication – not integration – of animals; you laud praise upon a forester for killing thousands of feral animals; you endorse snaring (without offering balanced explanation of why activists consider snare hunting particularly cruel); and you promote hunting – without addressing the concerns of your own constituency.

A majority of environmentalists offer a conscious, compassionate approach to the care of and respect for lives of animals. I am deeply saddened to learn that the approach you have now taken is not within this realm.

There is room on this island, on this planet, for plants and forests, for reserves, for humans and animals.

Kathryn Wiese Gibson

Co-publisher

Hawai`i Island Journal, Ocean View

Volume 10, Number 6 December 1999