Wednesday, April 26, 2017

Hawai`i tides running 8+inches higher than predicted--and this will go on for months.

Very strange stuff is going on at Hawai`i’s coastlines—sea levels have jumped in the past few months as much as they have in the past century.

Oceanographers are trying to figure out just what’s going on.

(Image: The pink to reddish areas in this graphic represent higher than normal sea levels. The blues are lower water. Credit: University of Hawai`i Sea Level Center.)

But what it means for now is that we are seeing eight to 10 inches higher high tides than we did a year ago.

If you’ve been at the docks, or at low-lying coastlines, you’ve seen it. This week will see some of the highest high tides.

University of Hawai`i coastal geologist Chip Fletcher said the superhigh water has been around for some time, and people seeing the unusual water levels and noting that it's strange are not mistaken.

“No it’s not a mistake - there has been a slug of high sea level for a year or more that has lingered around the islands,” Fletcher said.

Here is a graph that shows (red line) the actual sea levels, compared (blue line) to the normal predictions of sea levels. The waviness reflects tides. 

“Definitely an unusual event. We haven’t seen something like this during the past 20 years or so,” said Mark Merrifield, coastal geologist with the University of Hawai`i School of Ocean and Earth Science and Technology.

The good news is that this sudden increase may be temporary. Merrifield said some forecasts suggests the superhigh tides will last at least through the summer.

“Elevated sea levels around Hawaii are likely to continue through the forecast period, potentially enhancing extreme high tides during May, June, and July,” says this website from the University’s Sea Level Center. 

That doesn’t mean the high tides end in July—just that July is as far in the future as the forecast goes.

This is not a global phenomenon. The Pacific Ocean appears to be bumpy. The sea levels are higher in some areas (as around the Hawaiian Islands) and lower in other areas (In coming months, “sea levels are likely to be near or below-normal in the tropical northwestern Pacific {Yap, Guam, Chuuk, and Pohnpei} and above-normal in the equatorial central Pacific {Kiritimati}.”)

Merrifield said researchers are working to try to understand what’s going on.

Meanwhile, the background global sea levels continue to rise, and at an increasing pace.

This article from the American Geophysical Union says sea levels are now rising 25 percent faster than they were a quarter-century ago.

The article cites this study published in Geophysical Research Letters

The increase appears, the report said, to be “mostly due to Greenland mass loss increase and also to slight increase of all other components of the budget.”

The superhigh water of the past few months, on top of the increasing rate of sea level rise, puts the Islands at significantly increased risk from events that drive water ashore, like tsunami and major storms.


© Jan TenBruggencate 2017

Monday, April 17, 2017

Zika now spread by at least two Hawai`i mosquito species

Aedes aegypti biting a human.
(Modified USDA image.)
 Mosquitoes are not native to Hawaii, but we’ve got them, and new evidence is that they’re growing increasingly dangerous.

The Zika virus can be spread by at least two Hawai`i mosquitoes, including one of the most common species in the Islands.

We’ve got eight mosquito species now—there’s a list at the bottom of this post. Some diseases are spread by only one species—but that’s changing.

For example, it used to be believed Aedes aegypti, which has limited distribution in Hawai`i. But now Florida researchers working in Brazil found it has spread to the Asian tiger mosquito, Aedes albopictus, which is everywhere in the Islands.
that the Zika virus could only be spread by the Yellow fever mosquito,

Dozens of American babies have been born with severe birth defects associated with Zika, and the number of cases is growing. 

The most common defect is a deformed brain. Hawai`i has had 16 reported cases of Zika, according to the U.S. Centers for Disease Control.

Here’s the Science Daily report on Zika’s new host. 

“"These results are important because they are the first to show that Aedes albopictus can be infected with Zika virus RNA," said Chelsea Smartt, a faculty member at the UF/IFAS Florida Medical Entomology Laboratory in Vero Beach, Florida. "Also, this study found Zika virus RNA in male mosquitoes, which we can infer also means the Zika virus RNA came from the mother. We need to determine if live Zika virus can also be transmitted in Aedes albopictus."

And there is evidence that a number of other mosquitoes may also be capable of transmitting Zika, says the paper, which can be read here

Not to make too much of this, but two key weapons in attacking mosquito-borne illness are targeted insecticides and genetic modifications to impact mosquito populations. And in Hawai`i, both insecticides and genetic modification are being targeted by activists for entire bans or limitations on use of these products and technologies. Thus far, the Legislature and the courts have held off these movements.

Hawai’i’s four mosquito species that bite in the daytime are Aedes albopictus (Asian tiger mosquito), Aedes aegypti (Yellow Fever mosquito), Aedes japonicus (Asian bush mosquito), and Wyeomyia mitchelli (Bromeliad mosquito).

The two that bit at night are Culex quinquefasciatus (Southern house mosquito) and Aedes vexans (Inland floodwater mosquito).

There are a couple of other mosquitoes that don’t bite humans, so we won’t worry about them for this article.
More about these critters in the Islands at this Departmentof Health site

© 2017 Jan TenBruggencate


Sunday, April 16, 2017

A new look at Polynesian voyaging. After initial contact, maybe it was all about goods and services.

Polynesians maintained distant voyaging links through much of the history of their Pacific occupation.

It was a kind of connectivity that helped new island occupations succeed, and kept voyaging communities vibrant. And why? Some of it may have been just business--meeting the need for trade.

This ocean connection “was a deliberate enabling strategy essential for colonising the remote Pacific…this process played out on a canvas of different archipelagos with contrasting resources, both small and large islands, and with varying levels of ecological diversity and remoteness,” wrote Marshall Weisler and Richard Walter, in a new book, The Routledge Handbook of Archaeology and Globalization.

The evidence of the long-term connection between distant islands comes in many forms.

One example, of course, is a famous adze, sourced from a quarry on the Hawaiian island of Kaho`olawe, and found by archaeologists in the Tuamotu islands far to the south. It proved that the Polynesian voyaging that led to the discovery and population of the Hawaiian Islands was not a one-time accidental event, but that there were return voyages.

How important was that?

“One Tuamotuan adze was identified as originating from the Hawaiian islands, a distance of  ͠  4000 km—making it the longest known, continuous maritime trip in world prehistory,” they wrote.

In the Cook Islands, there was evidence of active trade. Basalt for adze blades has been found on coral islands without hard rock of their own. And pearl shell for fishhooks and scrapers has been found on volcanic islands where the pearl oysters didn’t grow. The assumption is that the fine-grained basalt and black-lipped pearl shell were traded by voyagers.

And there is also a strong oral tradition of voyaging that backs up the archaeology. In the Cooks, there are stories of the famous navigator-voyagers Tangi`ia, Karika and others. Hawai`i has the stories of Mo`ikeha and his voyaging son Kila.

Weisler and Walter argue that goods traveled back and forth, not only resupplying small island communities, but also bringing goods back to parent communities. The voyagers brought not only rock and shell, but planting material, volcanic glass for fine cutting, and even marriage partners.

Hawai`i even has a tradition of the priest Pa`ao, who felt Hawaiians were lacking adequate leadership, sailing to Tahiti to bring back a chief to rule them. The chief was Pilika`aiea.

For some islands, such voyaging was critical to the survival of the community. The small, isolated Pitcairn group could only have survived with the assistance of “repeated resourcing from the parent populations on Mangareva,” the authors wrote.

Not every island group had much to offer in material goods, but some had other values. The Tuamotu Islands, for example, have few resources, but they sprawl across the ocean, and they’re hard to miss. That being the case, they are a convenient stopping place to establish a voyager’s position, so it would have been valuable to keep their residents part of the “family.”

Hawai`i's voyaging canoe Hokule`a has regularly used the Tuamotus as an intermediate stop, to confirm the accuracy of navigation.

“There was little economic reason to travel to the Tuamotus, but their location made them a navigational screen that captured any movement in the region, and no doubt they benefited from this,” Weisler and Walter wrote.

Limits are one of the hallmarks of island societies. There is a point at which further population increase, or further drawdown of resources, cannot be sustained.

“In Mangareva during late prehistory food scarcities drove people to steal growing crops and rob breadfruit storage pits (the main staple), and there are even instances of fresh meat cannibalism and unearthing graves of newly buried corpses for food,” they wrote.

Some anthropologists argue that population pressure was a promoter of new voyaging, to find new islands and new resources. But perhaps the opposite was sometimes also true. Population pressure could have rendered voyaging difficult or inadvisable. 

“Constructing ‘expensive’ voyaging canoes and resourcing their crews was no longer a priority. Indeed, it was risky to leave agricultural lands unprotected to engage in long-distance voyaging trips,” Weisler and Walter suggest.

So, maybe islands full of people and short of resources caused societies to look inward instead of outward, ending the great Polynesian traditions of voyaging.

That said, the cultural memory of the voyaging days has resulted in a paradigm that still exists today. “Interaction and exchange is …a part of the fabric of Pacific life,” the authors wrote.


© 2017 Jan W. TenBruggencate 

Monday, April 10, 2017

Hawaiian pigs aggressive and spreading everywhere.

Everybody’s got a pig story.

Unless you live in a highrise or a yacht harbor, chances are you’ve come across some of the feral pigs that are increasing their range throughout the Islands, even moving into urban areas.

(Image: Feral pig with native ferns. Credit Hawaii Volcanoes National Park.)

People in the Hawai`i suburbs are waking to find their lawns chewed up. Gardens are at constant risk. Pastures are torn brown by hogs looking for worms and grubs.

In the forests, pigs create vast mudholes where native understory used to grow—a double threat, since not only are the native species destroyed, but it creates open ground for aggressive invasive alien plants to set root.

But what are these pigs? Is there something special about them?

A team of researchers late last year published a study on the genetic makeup of Hawaiian feral hogs in the journal Royal Society Open Science. The team, led by Anna Linderholm of Oxford and Texas A&M, took genetic samples from dozens of feral pigs from across the state.

They found that there’s still a lot of Polynesian pig in the genetic mix, but also evidence of multiple introductions of other porcine species, including the Eurasian boar, which—it is argued—made them more aggressive and invasive in the environment.

“Understanding the degree to which modern feral pigs retain their Polynesian ancestry and whether pigs introduced by Europeans have replaced those originally introduced will lead to more informed debates regarding the management of Hawaiian pigs,” wrote Linderholm and her group.

Pigs got to the Islands with Polynesian voyagers about 1200 A.D., the paper says. And then came Westerners, who also carried pigs on their vessels.

“Western explorers, like the Polynesians before them, traveled with and introduced domesticated plants and animals across the Pacific. In many cases, Westerners came into contact with local cultures that already possessed domesticated varieties of the same taxa that led to gene flow and possibly replacement,” the paper said.

In Tahiti, the local pig population got larger quickly when crossed with European stock—in as little as three years. The crossing has been extensive in Hawai`i as well, they wrote.

“The genetic evidence presented here indicates that the current Hawaiian feral pig population is a mixture of those brought to Hawaii by the Polynesians and pigs of European (and possibly Asian) origin introduced to the islands much later,” they wrote.

All but a couple of the pigs they sampled had some Polynesian pig genes. That couple was pure European. But it is clear that some of the traditional Polynesian genetics is still in most Hawaiian feral pigs: "The predominance of the Pacific clade haplotypes ... suggests that the original Polynesian lineages have not been completely replaced by more recent introductions."

The authors are careful not to suggest that its only breeding that is making pigs more common and widespread. The Hawaiian environment of the pre-European period might not have been as conducive to pig survival. But the arrival of a lot of fleshy fruits (banana poka, strawberry guava and the like), and the appearance of earthworms—which are not native to the Islands—helped make the Hawaiian forest a lot tastier, they said.

“And though the issue of whether the first pigs on Hawaii became feral prior to the arrival of Europeans remains contentious, extensive damage to native habitats by feral pigs appears to be recent. In fact, it was probably not until the twentieth century, with the introduction of new sources of protein such as earthworms and invasive fleshy-fruited plants that pigs were able to thrive in the forests, thus becoming a significant problem to the native flora and fauna,” they wrote.

Feral pigs are a problem in many parts of the world. They’re increasing their range on the Mainland as well, where they can be a major threat to established agriculture—chewing up corn fields and other crops. Pigs are Eurasian, originally, and didn’t appear in the Americas until the mid-1500s. Here’s a report on problems in Virginia. 

A team led by Pamela Scheffler wrote in 2012 about pig density in Hawaiian forests here. They found a direct correlation between increasing numbers of pigs and decreasing levels of native plants. The explanation in the paper is pretty damning.

“In Hawai‘i, feral pigs can be considered ecosystem engineers due to the changes they catalyze in Hawaiian ecosystems. They root and trample soils, disrupting soil microarthropod communities, leading to potential seedling mortality, and to reduced plant species richness. Feral pigs also eat or otherwise destroy native vegetation; cause changes in soil; act as dispersal agents and create habitat for exotic plants. They also create mosquito breeding habitat by knocking over and hollowing out troughs in native tree ferns and making rain-filled wallows.”


© Jan TenBruggencate 2017

Sunday, March 19, 2017

Spiders are your friend, if you don't like all the other creepy-crawlies

So if you live in the Islands, you’ve got geckos in your house, and they’re annoying. But just how many insects are they removing to survive?

Probably a lot—and that’s a good thing for both your sanity and your health.

It turns out the spiders around your home, similarly annoying, are also removing insects from the environment—a lot of insects.

(Image: You won't find this one around your home. It's a sea spider, photographed by teacher Kaitlin Baird from a NOAA bottom trawl. Sea spiders are deep water creatures that tend to have very long legs and tiny bodies. Credit: Kaitlin Baird/NOAA.)

Globally, spiders are taking out 400 to 800 million tons of insects. A stunning amount.

That’s from calculations done by the authors of this paper

(Okay, we ought here to clarify that spiders are not themselves insects. Spiders are arachnids, and they have two main body parts and eight legs. Insects are six-legged creatures with three main body parts. There are other differences as well, but that should suffice for this discussion.)

Spiders have a much bigger impact in natural environments than disturbed or urban environments, but, still. They account for a lot of pest control.

One of the findings of the paper above is that if you remove spiders from the environment, you can expect a big rebound in insect populations.

“Our estimates are supported by the published results of exclusion experiments, showing that the number of herbivorous/detritivorous insects and collembolans increased significantly after spider removal from experimental plots.”

(Yeah, collembolans. Six-legged critters that used to be considered insects but no longer are. Commonly called springtails, for their prodigious jumping capacity.)

You may worry about predators like sharks and bears and snakes and mosquitoes, but spiders, say authors Martin Nyffeler and Klaus Birkhofer, are “the most common and abundant predators in terrestrial ecosystems.”

The Eurekalert press release on their study is here. 

If you have spiders in your garden, think twice before removing them. All spiders are carnivores—they eat other creepy-crawlies and only very rarely will one munch a plant.

Hawaii has lots of introduced spiders, but its native spiders are a fascinating bunch. The happy-faced spider is perhaps the most famous, but there are lots more. The Nature Conservancy’s Sam Gon writes about some of them here

If you’re interested in the tiny critters of the island, I can recommend “What’s Bugging Me,” by Gordon M. Nishida and Joann M. Tenorio. And "What Bit Me?" by the same pair.



© Jan TenBruggencate 2017