Which brings to mind something they did on Lana'i. A botanist figured out that Cook (or is it Norfolk) pines have the ability to draw an astounding amount of extra moisture out of the air compared to what there would be without these trees. The upcountry of Lana'i received plantations of these "pines" and it transformed the microclimate from hot and dry to misty and drippy. So I was told when I visited there.
But not just any trees have this property. These trees in particular.
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Since these islands started out as smoking piles of cinders, clearly orographic lift alone is enough to produce SOME rain. I do get the message however that even if the trees-make-rain thing is bunk, if enough people think it is true and have enough clout they might push for laws or restrictions in desparation, so any verifiable evidence could cause a disproportionate reaction.
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Rain on the island comes from two sources--offshore maritime air, and from the island itself, from freshwater evaporation of moisture already on the island. Most of the rain that makes the Kona side, it seems to me, to be of the later sort. Evaporation rainfall is heavily influenced by vegetation. That much is obvious to a child. Roads dry out first and fast, and the water runs off them into the sea. Forests stay cool and wet in all but the most extreme circumstances.
If you ask "do tree grows where the rain falls" or "does the rain fall where there are trees"--if you don't realize both propositions are necessary to understanding the system, you miss the central tenet of modern climate science.
There will be people who argue both ways for sure. My main point in bringing up the post is as Mark observes--the reality here may be pointless, as the perception of an effect is as important as the evidence.
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Here an interesting article on the subject of Hawaiian forests. Jan Tenbrugencate has written about Hawaiian culture and science for the Advertiser for years.
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Somewhere i read that Kahoolawe when it was forested 200 or so years ago before it was deforested by people introducing livestock to the island, there was a large cloud that ran from maui and covered Kahoolawe often.
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I attended a forum at the mokupapapa discovery center where this was the subject addressed. The speaker was Dr. Juvik From UHH who is basically the Guru of this subject. He said that that one could pave the mountains from top to bottom and we would still get 150 inches of rain. The rain causes that plants to grow, plants don't make rain. He did mention that in areas where there is fog, condensation occurs on trees dripping down to add the the percipitation. You will notice on saddle road green rings under some trees as evidence of this. But the fact is the mountain makes the difference, not the trees. Don't get me wrong, I love the trees, they make living here so nice, but their effect on the rain is minute.
Daniel R Diamond
I'm gonna have to go with Daniel on this one. All of the Hawaiian island, to some extent, enjoy what's known a the the "rain shadow" effects of the volcanos and/or the dormant volcanos. There was much research to support Dr. Juvk's position gathered from the Mt. St. Helens erruption and the barren topography that was left behind.. Kauai, the wettest place on earth, has undergone substantial growth on it's east coast and I seriously doubt if it has effected the rainfall on the western side of the island. It seems that all through the state from Barking sands to the Moloka'i Ranch the western sides of the island has "historically" been dry thus one would think that would support the concluision of Dr Juvik. Peace, dave
Blessings,
dave
"It doesn't mean that much to me.. to mean that much to you. Neil Young
Blessings,
dave
"It doesn't mean that much to me.. to mean that much to you." Neil Young
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No one is denying the existence of a rain shadow effect. But, as every good sailor or glider pilot knows first hand, when you clear ground, you get a lot more thermals. The trick to long distance gliding is to hop-scotch from one to the next. These thermals unquestionably break away moisture and thus potential rainfall, by blasting hot air up through the TWI, which then is lost by the upper level trades. While the leeward sides are/and have always been dry, they are now drier then they've ever been, and people are looking for reasons why.
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Oh Boy. An argument on science. I take some pride in the quality of debate on Punaweb. We don't spend much time bragging about our stock picks or the price of real estate. I am grateful.
(Sorry for the brief hijack) Keep it up.....
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Assume the best and ask questions.
Punaweb moderator
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Anyone have access to historical rain data for Hawaii? It would be interesting to see what happened when large land tracts were put into sugar production and then later when that industry died.
Puna: Our roosters crow first
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I have seen pictures of areas on Oahu that are now heavily forested that were barren back in the 1800s. Sorry, I can't remember the specifics but I remember going, WOW, big difference from today. I think it is true that at least in certain areas of the contry forest cover has increased in recent decades as small local farms have decreased. I know this is true of New York State and apparently true of Hawaii. To do the analysis right we would need to quantify forest cover in Hawaii over the last few hundred years. What impact did ancient Hawaiians have on forest cover? The Easter Islanders certainly had a profound effect on their environment.
In the last 50 years forest cover may have started to increase again. It has in other parts of the country.
