{"id":427,"date":"2014-08-26T11:53:08","date_gmt":"2014-08-26T11:53:08","guid":{"rendered":"http:\/\/teresadawson.wordpress.com\/?p=372"},"modified":"2014-08-26T11:53:08","modified_gmt":"2014-08-26T11:53:08","slug":"symposium-looks-at-history-of-threats-to-and-hopes-for-hawaiis-remnant-dry-forests","status":"publish","type":"post","link":"https:\/\/environment-hawaii.org\/?p=427","title":{"rendered":"Symposium Looks at History of, Threats to, and Hopes for Hawai`i's Remnant Dry Forests"},"content":{"rendered":"

Peter Vitousek didn\u2019t mince words: \u201cEverything we\u2019ve lost, and everything we will lose, is because of human activity. We\u2019re responsible for that change.\u201d<\/p>\n

Vitousek, a professor of biological sciences at Stanford University, made the comments as the opening speaker at the seventh annual Nahelehele Dryland Forest Symposium, held March 1 at the King Kamehameha Hotel in Kona. Addressing the crowd of scientists, resource managers, volunteers, and others concerned with protecting these rare ecosystems, Vitousek linked the decline of dry forests in Hawai`i to their loss globally and sought to inspire those in attendance with \u201csomething of a revival meeting to remind us of the importance of what we\u2019re doing.\u201d<\/p>\n

\u201cThese forests are widespread,\u201d he noted. The conditions that occur in Hawai`i that led to the growth of dry forests occur elsewhere in the world, he said, adding that their very definition \u201cimplies several features that make them vulnerable:<\/p>\n

\u201cTheir soils are typically more fertile than soils of rainforests. That makes sense, because soil fertility is governed in part by how much water passes through soil, leaching nutrients out\u2026.<\/p>\n

\u201cAlso, the long dry season means fire can be used in forest clearing. It\u2019s a lot easier to clear a forest if you can use fire, even though some forests are quite resistant to fire if they\u2019re intact.<\/p>\n

\u201cLong dry seasons help cultivators control weeds and pests, so they\u2019re better suited to intensive agriculture\u2026.<\/p>\n

\u201cDisturbance and seasonal variation support more biological invasions. Speaking globally, \u2026 a really widespread invader is tropical grasses.\u201d<\/p>\n

As a result, Vitousek said, \u201cwhat you see if you look at deforestation globally is arcs of deforestation that are taking place around the great rainforests \u2013 not the centers of rain forests but their drier margins, which are more suitable than fain forests for clearing, easier to clear, easier to keep clear, and more suited to various kinds of human land use\u2026 What\u2019s left are rocky sites too hard to farm once you\u2019ve cleared them \u2026 and very small protected areas.\u201d<\/p>\n

Vitousek pioneered the study of rain-fed agricultural systems in North Hawai`i, particularly on the leeward slopes of Kohala mountain where the miles-long walls, the remains of thousands of agricultural fields, still show up clearly in aerial photographs. \u201cThese areas were farmed very intensively by Hawaiians,\u201d he noted, especially areas receiving from 30 to 70 inches of rain annually.<\/p>\n

\u201cIt was mesic to dry forest when the Hawaiians began cultivating it,\u201d he said. The soil in these areas is \u201cextraordinarily rich compared to either wetter or drier areas, and it got so rich because the forests that grew there before clearing were extremely deep rooted\u2026 They persist through the dry season by having deep roots, and in the process of pumping up deep water they pump up nutrients. What makes this area so rich is tens of thousands of years of them pulling nutrients from the soil and depositing them on the surface.\u201d<\/p>\n

Through carbon dating of charcoal deposits found in a trench excavated by Vitousek\u2019s alma mater, Hawai`i Preparatory Academy in Waimea, it was possible to obtain an idea of just how recently the dry forests in the area were cleared.<\/p>\n

\u201cThe maximum age for this charcoal was 450 years,\u201d Vitousek said. \u201cThis was a dry forest cleared for agriculture in this area of high soil fertility, created by the dry forest itself. It wasn\u2019t something killed by rats. It is something that only 450 years ago or less, when agriculture was being intensified in the place, was cleared by Hawaiians.\u201d<\/p>\n

Setting the dry forests of Hawai`i island apart from those on other islands was the young age of the land itself. \u201cThese dry forests that created the sweet spot of soil fertility that Hawaiians found when they cleared and cultivated them \u2026 were rich enough for intensive agriculture and low enough in elevation so Hawaiian crops could grow,\u201d he said. \u201cWe also have beautiful dry forests on Kaua`i, in the Wai`anae range, and in areas that get 50 inches of rain or less a year. They have deep soils, but the fertility is much less than elsewhere. They\u2019re tremendously infertile. That\u2019s because they have been sitting there for thousands of years, they\u2019ve had nutrients pumped out by the dry forests for millions of years. So those areas are not really suitable for intensive agriculture, as are the newer soils of Kohala.\u201d<\/p>\n

\u201cThe dry forests we have now, the dry forests we\u2019re working with here, are beautiful and spectacular,\u201d Vitousek said. \u201cBut they\u2019re not the universe of dry forests that were here before. They\u2019re remnants. There are parts of that universe we just don\u2019t see anymore. And that\u2019s all the more reason to keep the ones we have, to do the work we\u2019re doing.\u201d<\/p>\n

\u201cThe efforts going on here at Ka`upulehu or Mahaulepu or Kanaio or Auwahi, where all of you are working to keep these dry forests alive or to restore them, are on the leading edge of a global challenge\u2026. It\u2019s still the anthropocene era, but the anthropocene can be an era of stewardship as well as an era of loss\u2026. What we do, how we work to sustain these forests is something the world can use as well.\u201d<\/p>\n

A Tortoise Monastery on Kaua`i\u00a0<\/i><\/b><\/p>\n

Vitousek spoke of the anthropocene era, one in which the human species has emerged as a significant force capable of reshaping the face of the Earth.<\/p>\n

But on a small patch of land along Kaua`i\u2019s southern coast, tortoises have become the agents of change.<\/p>\n

David Burney, a paleoenvironmentalist with the National Tropical Botanical Garden, has rescued abandoned giant tortoises from across Hawai`i and put them to work clearing weeds from an area where he and others are attempting to restore a dry coastal ecosystem.<\/p>\n

Much of Burney\u2019s work has been below ground, in Makauwahi cave, the largest limestone cave in Hawai`i and possibly the richest fossil site in the entire Hawaiian chain. \u201cWe realized early on, working with Helen James and Storrs Olsen \u2026 that the feeding guilds that are missing are the predators, the terrestrial herbivores, the terrestrial omnivores. They\u2019re almost entirely absent from native habitats today,\u201d he said. \u201cThat started us thinking, particularly about herbivores.\u201d<\/p>\n

One of the largest of these birds, he continued, was the turtle-jawed moa nalo. \u201cIt truly had a tortoise-like beak \u2026 and would have been the biggest thing around on land. They probably had no natural enemies as adults because they were so much bigger\u2026. So we started thinking about that.\u201d<\/p>\n

Then, on a visit to the island of Rodrigues, in the Indian Ocean, Burney observed a restoration effort that avoided what he called the \u201cweed treadmill\u201d that so often discourages restoration efforts in Hawai`i \u2013 where no sooner are weeds pulled than another one takes its place. As soon as an area is planted in Rodrigues, however, \u201cthey fence the area, put in giant tortoises, and walk away. The tortoises do the weeding and fertilizing, and germinate seeds by eating fruits.\u201d<\/p>\n

Burney noticed also the presence of several native Hawaiian plants, which, he said, \u201chad become mildly invasive.\u201d<\/p>\n

That got Burney and his colleagues thinking about the \u201ctoothless islands\u201d of the West Indies, Melanesia, and Hawai`i. \u201cOur plants are not defended against animals with teeth and advanced stomachs,\u201d he said. \u201cBut they do have defenses against creatures with beaks, toothless creatures.\u201d<\/p>\n

Tortoises, it turns out, \u201chave no interest in native plants,\u201d Burney said. \u201cThey have something about them that they don\u2019t like, in terms of defense compounds, growth habits, et cetera.\u201d<\/p>\n

\u201cOne year and eleven giant tortoises later,\u201d he continued, \u201cwe cast our lot with the Humane Society and the Turtle Conservancy. We discovered there are hundreds of giant tortoises right here in Hawai`i already. They got here through the process of looking cute in pet stores.\u201d<\/p>\n

The animals are unlikely to become invasive pests, Burney said. \u201cThey can\u2019t breed here. The temperature of the soil is too low for them, and if any of the eggs managed to hatch, they\u2019d all be males anyway. We\u2019re running a tortoise monastery.\u201d<\/p>\n

The worst that tortoises can do to native plants is to crush them. \u201cIf you plant natives, let them get up to some size\u201d before unleashing the tortoises on them, he said.<\/p>\n

Only one weed seems resistant to tortoises \u2013 the thorny Mimosa pudica, also known as the sleeping plant for its habit of curing up its leaves in response to touch. The tortoises aren\u2019t put off by the thorns, Burney said, and are happy to munch on it when it is already dead. Rather, they seem to be spooked by the sudden movement of the living plant.<\/p>\n

When Burney\u2019s talk was finished, one member of the audience raised the question that seemed to be on everyone\u2019s mind: \u201cHow many tortoises per acre are needed to keep the weeds down?\u201d Burney was asked. It depends on the size of the tortoises, he replied, noting that they continued to grow throughout their lives. But, if you have medium-sized tortoises, about six of them per acre should keep the weeds at bay, he answered.<\/p>\n

Threatening Thrips<\/i><\/b><\/p>\n

A new-to-Hawai`i species of thrips is preying on the native naio, or false sandalwood (Myoporum sandwicense<\/i>), with a mortality rate that is up to 90 percent in some areas.<\/p>\n

That was the grim report from Cynthia King, an entomologist with the Department of Land and Natural Resources\u2019 Division of Forestry and Wildlife.<\/p>\n

The thrips was first observed in the winter of 2008 by landscapers on the Big Island, she said, and was officially reported by the Hawai`i Department of Agriculture in 2009. In May of that same year, the DOA stopped the inter-island movement of naio, but by then it was already widely spread across the Big Island.<\/p>\n

The species was first detected in 2005 in California, where it continues to devastate Myoporum trees. \u201cAt the time it was discovered in California and Hawai`i, we didn\u2019t know where they were from,\u201d King said. \u201cWe suspected the Australia-New Zealand region, since that\u2019s where Myoporum diversity is highest.\u201d<\/p>\n

Eventually, researchers tracked the thrips to Tasmania. \u201cSo, from Tasmania it went to California, and from California to here,\u201d King said, almost certainly in a shipment of landscape material.<\/p>\n

The thrips affects the growing terminals of the tree, King noted, and infestation rates are increasing across all sites where the thrips is found. And as the infestation rates increase, \u201cso, too, are dieback rates\u201d on the rise, she added.<\/p>\n

King listed some of the potential impacts if the thrips is not controlled. One of the biggest impacts, already being seen in dry forest restoration efforts on the Big Island, is the exclusion of naio from replanting schemes. \u201cNaio has been a great go-to plant as far as outplanting and restoration efforts are concerned,\u201d King said, \u201cbut I know on the Big Island, folks are already adapting their strategies.\u201d<\/p>\n

Other possible impacts cited by King include:<\/p>\n