Miconia

Tiny golden butterfly could help halt miconia invasion

Posted on April 28, 2020 by Lissa Strohecker

Caterpillars of the golden miconia butterfly can only survive on miconia and related plants. The caterpillars get together in clumps and devour the leaves. In doing so, they may reduce the damage miconia can cause in the rainforest. — PABLO ALLEN photo

In the hills above Hāna, Nāhiku, and Keʻanae, the Maui Invasive Species Committee (MISC) crew hikes day in and day out looking for and pulling miconia plants. The team is about to grow as a kaleidoscope of golden yellow butterflies descends to assist with control.

Miconia is a notorious invader of Hawaiian forests. A single plant can produce 8 million seeds. Miconia seeds grow quickly into large plants with huge leaves that block out the sunlight preventing other plants from germinating. Miconia’s shallow roots do little to stabilize the soil. Eventually, miconia becomes the only plant in the forest; invaded sites are known for landslides and erosion that muddies streams and buries reefs.

Sam Akoi III pulls miconia from the ground in 2003. The shallow roots make the plant easy to pull but miconia does a poor job holding soil. Invaded forest slopes are prone to erosion–MISC file photo

When biologists first found this invasive plant growing in Hawaiʻi, it was a call to action. Retired state forester Bob Hobdy helped address miconia in East Maui in the early 1990s. Initially, crews focused on the area above Hāna known as “the core,” but reports started pouring in from multiple locations across East Maui. “The idea of eradication [removing every plant from the island] was set aside,” says Hobdy. “It was not feasible.” The shrubby tree was scattered from Huelo to Kipahulu, with two major infestations in Nāhiku and Hāna. Too widespread to eradicate, but too damaging to ignore, the long-term solution was biocontrol: the researched introduction of a natural enemy specific to miconia that could lessen the impact and spread of the plant.

Over the last 27 years, crews have worked to contain this invader in the field. It’s been a success: miconia never reached the West Maui mountains and it’s rare to find a plant along Hāna Highway. Meanwhile, researchers in Hawaiʻi and South America have sought out and tested insects and plant diseases in hopes of finding something that will permanently undermine the plant’s invasiveness.

In 1997, ecologists released a fungus that eats holes in miconia’s large purple leaves. In Tahiti, this fungal natural enemy opened up the canopy so that other plants could grow, but fungus didn’t have the same effect here in Hawaiʻi. The search continued.

Tracy Johnson of the U.S. Forest Service has worked to find miconia’s natural enemies for 20 years. He’s hopeful about another miconia pests, a tiny yellow butterfly that lays its eggs on the leaves. The caterpillars hatch out and to dine on the umbrella-like leaves until they become adults. “Itʻs very specific to miconia,” says Johnson. “We know from observation in Costa Rica and in Hawaiʻi that it’s one of the most damaging insects to leaves of the plant.”

Miconia’s huge leaves are major problems: they act like tarps, shading out the understory, collecting raindrops and funneling them to the ground. In comparison, native ōhiʻa and koa trees have clusters of little leaves that break up rainfall into small drops that gently water the understory. The raindrops that roll off of miconia leaves are some of the largest measured They hit the ground with extra force—and since the ground beneath miconia is bare—they contribute to increased erosion. In fact, scientists have found that erosion is greater in a miconia-invaded forest than if the rain fell on bare soil.

“Itʻs (the golden miconia butterfly) very specific to miconia,” says Johnson. “We know from observation in Costa Rica and in Hawaiʻi that it’s one of the most damaging insects to leaves of the plant.”

Though only the size of your fingernail, the golden miconia butterfly could have a big impact on invasive miconia. Native to Costa Rica, these butterflies could be a welcome addition to miconia control efforts here in Hawaiʻi. — KENJI NISHIDA photo

Enter the golden miconia butterfly, Euselasia chrysippe, —a voracious leaf eater. Johnson and colleagues from the University of Costa Rica tested E. chrysippe with 73 different plants to see what the caterpillars would feed on. In a process called no-choice testing, caterpillars are placed in a petri dish with a leaf of the plant being tested. When forced to feed on other plants, they died; only Miconia calvescens and closely related plants in the melastome family can sustain them. This is good news since Hawaiʻi has no native melastomes.

After gorging on miconia, E. chrysippe caterpillars metamorphose into butterflies and seek out another miconia plant on which to lay their eggs. Like the MISC miconia crews, they’re really good a finding the pesky plant.

The golden miconia butterfly could help halt Hawaiʻi’s miconia invasion. But there is still more to be done. Johnson is investigating other potential natural enemies, particularly an insect that eats miconia seeds. Until a suite of effective and safe natural enemies exists to control miconia, crews from MISC will continue combing the hillside in search of miconia. Any sightings of miconia can be reported to MISC at 808-573-6472.

April 2020 Update: The Hawaiʻi Department of Agriculture is soliciting comments on the draft Environmental Assessment for the release of the golden miconia butterfly. Comments are accepted through May 26, 2020. HDOA press release

Lissa Strohecker is the public relations and education specialist for the Maui Invasive Species Committee. She holds a biological sciences degree from Montana State University. Kia’i Moku, “Guarding the Island,” is prepared by the Maui Invasive Species Committee to provide information on protecting the island from invasive plants and animals that can threaten the island’s environment, economy, and quality of life.

This article was originally published in the Maui News on July 8th, 2018, as part of the Kia‘i Moku Column from the Maui Invasive Species Committee.

Drones help field crews find invasive species

Posted on November 22, 2017 by Lissa Strohecker

Would you rather walk across this lava field to look for invasive plants or search by air? Drones are increasing the efficiency of invasive species field crews on Hawaiʻi Island. Photo by T. Sullivan, BIISC.

Your mission: find a few invasive silk oak trees scattered across a 35,000-acre ancient cinder cone that resembles a bundt cake. Dead-ends and backtracking are the norm as you navigate up and down and across the slope, trying to locate and reach the trees.

Such is the task facing the crews of the Big Island Invasive Species Committee (BIISC) as they endeavor to control silk oak trees on the slopes of Puʻu Waʻawaʻa (literally translated to “many furrowed”) near Kona. They now have help from a set of eyes in the sky.

Using a drone, or unmanned aerial vehicle (UAV), the crews can find the best path across the landscape, saving time and allowing them to more efficiently do what they do best: get rid of invasive plants.

“It works best on a large landscape,” explains Timo Sullivan, BIISC’s early detection and remote sensing specialist. “You can trade 8 hours of hiking for 2 hours of controlling,” he says. Sullivan’s work with BIISC began a few years ago when they were exploring ways to identify invasive Australian tree ferns hidden within vast eucalyptus plantations. Today, the drone is almost a part of the field crew, scouting out the best route or even finding plants the crew is searching for.

Timo Sullivan uses drones to help the field crews from the Big Island Invasive Species Committee find invasive plants. Photo courtesy T. Sullivan, BIISC.

“It works best with species you can see above the canopy” he says. BIISC relies on UAVs to help survey for rapid ʻōhiʻa death, a fungal disease affecting ʻōhiʻa trees on Hawaiʻi Island. The main symptom: the leaves turn brown almost overnight, as though frozen in place. “It’s surprisingly hard to tell if a tree in the canopy is dead when you are on the ground,“ says Sullivan.

Typically, he arrives at a field site a few hours before the crew and spends an hour flying the drone, followed by an hour viewing the footage on the laptop. Then the crew can head straight to the plants on the ground. It’s possible for Sullivan to cover 40 acres in an hour. This is a big shift from the past efforts where crews spent all day hiking to find maybe 10 plants. “It’s been a huge morale booster,” he says. “Crews feel more successful when they can actually remove plants rather than search for them all day.”

The drone BIISC uses is nothing fancy, just a consumer model with a GoPro attached to record what’s seen. The footage can be reviewed on the spot or later. Instead of three sets of tired eyes scanning from a helicopter, the footage can be shared with many, including researchers looking at native plants or other aspects of the landscape. A manager can see what the crew faces, as well as document change over time.

The technology has limitations though: searching for plants under the canopy is still a task for ground crews, and the drone has to remain in the line of sight of the operator. Surveying in Kīpahulu valley while sitting miles away in Makwao is currently not possible.

Miconia (circled in red) has large leaves with a distinctive leaf pattern. Researchers at the University of Hawaiʻi are looking at ways to train computers to analyze drone footage to find miconia. Photo courtesy of T. Sullivan, BIISC.

Researchers are investigating ways to take drone usage to the next level. Roberto Rodriguez, a PhD student at the University of Hawaiʻi-Manoa is helping to determine the ideal speed at which to review footage. Heʻs researching computer programs that analyze the footage. “Miconia is a nice initial plant to work with,” he says. “The large leaf size and distinct vein pattern is something a computer could identify.” They researcher can then take what they learn and modify it for other species.

Ground crews can’t hang up their boots entirely. They can’t get ahead of an invasive species’ seeding cycle until they remove every young plant before it goes to seed—and small understory plants typically aren’t visible from the air. Drones are just another tool. There may come a day when crew each has its own drone, enabling workers to easily glance at a gulch or a steep, inaccessible cliff to make sure no invasive plants remain.

To learn more about research and drone usage for conservation in Hawaiʻi check out http://spatial.uhh.hawaii.edu/index.htm.

This article was originally published in the Maui News on April 9th, 2017 as part of the Kia‘i Moku Column from the Maui Invasive Species Committee.

A Haʻiku gulch full of suprises

Posted on July 24, 2015 by Lissa Strohecker

The prickly seed ponds on this climbing vine led to a concernd Ha'iku resident reporting it to MISC as a potential invader. Turns out it is a native plant, Mucuna sloanei. Photo by Hank Oppenheimer

The prickly seed pods on this climbing vine led to a concerned Ha’iku resident reporting it to MISC as a potential invader. Turns out it is a native plant, Mucuna sloanei. Photo by Hank Oppenheimer

“Anything that bristly has got to be invasive,” said the Haʻiku resident who reported a vine that she found in the gulch on her family property. She called the Maui Invasive Species Committee (MISC) when neither she nor her relatives could identify the strange climber with seedpods covered in fiberglass-like hairs. No one in the family had noticed it before and they had worked or played in the gulch since small-kid times. She collected a specimen, prickly seedpods and all, and brought it into the MISC office.

Though bristly, it turned out not to be an invasive species after all. The unusual creeper was a native plant once widespread in low elevations on Maui and other Hawaiian Islands. Commonly known as seabean, botanists call it Mucuna sloanei.

Mucuna comes in two varieties: sloanei, indigenous to Hawaiʻi; and persericea, endemic to windward East Maui and found nowhere else in the world. There are only a few of the persericea plants left. Because of the rarity of the persericea variety, and the damage caused by pigs and cattle to its habitat, the vine was recently listed as endangered by the U.S Fish & Wildlife Service. The possibility that it could be thriving in a Haʻiku gulch, only a stone’s throw from the Haʻiku Marketplace, was therefore pretty exciting. But it takes an expert to know the difference between the two varieties and Hank Oppenheimer fits the bill.

Oppenheimer is the Maui Nui Coordinator for the Plant Extinction Prevention Program (PEPP), a Pacific Cooperative Studies Unit project that works to protect the most rare and threatened plants in Hawaiʻi. Throughout the state, a handful of people like Oppenheimer and technician Keahi Bustamente hike deep into remote forests, scaling cliffs and doing whatever they can to prevent the rarest species’ extinction. This includes collecting seeds from rare Hawaiian plants, propagating them in greenhouses, and then outplanting the precious plants in protected habitat.

For plants, garnering listing as a PEPP species of interest is a mixed blessing; it means there are less than 50 individuals left in the wild. Oppenheimer is investigating the distribution of persericea to determine if it should be included with the other 236 PEPP targets.

Finding the native Mucuna sloanei was a pleasant surprise. Photo by Hank Oppenheimer

Oppenheimer and Bustamente headed to the Ha’iku gulch. The vine turned out to be the more common sloanei, but Oppenheimer was still excited. “It was really interesting to see Mucuna in a place like that,” he said. Most of the habitat for Mucuna has been turned into pasture, farmland, or long ago taken over by invasive plants.

But as the team was leaving the gulch, they made a troubling discovery. Bustamente noticed an unusual plant with massive 2-3 foot long leaves, purple on the underside. He knew it instantly as miconia. This notorious pest and MISC target was certainly out of place; miconia is primarily between Keʻanae and Hāna. The discovery marks the westernmost naturally occurring plant in recent history.

So when the Haʻiku resident reported what she thought was an invasive vine, she actually helped uncover a relatively rare native species as well as one of the most invasive plants in Hawaiʻi. A great example of the more you look, the more you find.

Can you spot the miconia plant? The characteristic large leaves with purple undersides cued botanists into this plant’s presence in a Ha’iku Gulch. MISC file photo

To learn more about the Plant Extinction Prevention Program, visit the website www.pepphi.org. And if you think you may have Mucuna on your property, contact Hank Oppenheimer at henryo@hawaii.edu. If you would like help identifying an unusual plant, native or not, you can find a number of resources available online, including the Flikr site “Hawaii Plant ID,” curated by some of the state’s best botanists, or you can call MISC at 573-6472, particularly if you think you’ve found miconia.

Originally published in the Maui News, April 12th, 2015 as part of the Kia‘i Moku Column from the Maui Invasive Species Committee.

Invasive plants=Less water

Posted on June 27, 2014 by Lissa Strohecker

This rainforest, in Puu Kukui on West Maui, is an example of an open canopy rainforest typical of native rainforest in Hawaii. This forest acts like a ‘sponge,’ absorbing water from rain and gently releasing to recharge streams and aquifers. MISC file photo

When rain falls from the sky by the bucket-load it can be tempting to take water for granted, but the trip from raincloud to tap relies on effective, functioning natural systems. In Hawai‘i, alien plants disrupt the forest’s ability to capture water.

Water follows a cycle through the environment. Water over the ocean evaporates becoming atmospheric moister, as it travels over land it condenses into clouds, falling to Earth as rain or fog drip. Once on the ground, water has three paths: 1) it’s taken up by plants that use it to move nutrients through their cells, then return it to the atmosphere via transpiration; 2) it fills streams, lakes and rivers, eventually returning to the ocean–minus what was used for irrigation or lost through evaporation; or 3) it seeps through the soil into underground pools called aquifers. These aquifers supply most of the water we use to drink, bathe, and grow our food.

Forests have evolved differently to take advantage of prevailing water cycles in their regions. In South America and Africa the greatest diversity of plants is found up in the canopy. In Hawai‘i most plant species are found in the lower third of the forest, closer to the forest floor. Hawaiian understory plants need sunlight filtering through an open canopy. Koa and ‘ōh‘ia, the dominant Hawaiian canopy trees, grow in such a way that light reaches the shrubs and groundcover below.

Koa and ‘ōh‘ia pull water from passing clouds as fog drip; the curved leaves of koa provide surface area to collect moisture from clouds and channel it down leaf tips to the forest floor. Spongy plants on ‘ōh‘ia branches and trunks absorb moisture from passing clouds. Alien species disrupt the system.

Strawberry guava, Psidium cattleanium, has invaded Hawaiian rainforests, growing so dense and so

Strawberry guava invaded forest in Makawao Forest Reserve

The invasive tree strawberry guava chokes out native plants. As it sheds bark, strawberry guava provides no habitat for the plants growing on the trunks of native species. Photo courtesy of Forest and Kim Starr.

fast that it chokes out other plants. A strawberry-guava-invaded forest captures water differently than our native forests. In Hawai‘i Volcanoes National Park researchers found that a forest dominated by strawberry guava delivered less water to the forest floor than an intact native rainforest. Researchers noticed several differences between the two forest types: more rain ran down the stems of strawberry guava than ‘ōh‘ia but less water was pulled from the passing clouds. This could result from structural differences. ‘Ōh‘ia have aerial roots and furrowed bark carpeted with mosses and small plants called epiphytes. The epiphytes and aerial roots soak up water from passing clouds. Strawberry guava bark is smooth and regularly shed; few plants grow on its trunk and branches.

Other invasive species disrupt the water cycle by sheer size—leaf size. Miconia trees with three-foot long leaves sweep into the forest, stealing light from the understory and transforming it into darkened forest, the soil bare but for miconia seedlings. As another researcher on Hawai‘i Island discovered, the huge leaves are more than just light-hogs. They collect water as if they were huge tarps, and, as anyone who has stood near the edge of a tarp in a rainstorm knows, it’s only a matter of time until the water

The forest floor under a miconia invasion is bare, often with exposed roots. Not a good sign for water collection. MISC file photo

dumps down. The drops running off of miconia turn out to be the largest drops ever measured. Larger drops hit the ground harder, and where miconia has smothered the understory, those drops fall on bare soil. Huge drops compact soil particles, preventing water from seeping down to aquifers, instead causing it to run off, carrying topsoil into streams and eventually the ocean where it can smother coral reefs.

These are only some of the ways invasive plants alter the forest’s ability to capture water. Water-hungry plants like Himalayan ginger pave the forest floor in tough roots. Huge trees like eucalyptus require more water to carry nutrients to their crowns than smaller trees. Unfortunately, the list goes on. Healthy forests mean reliable sources of water. Keeping invasive plants out of native forests is one way to help keep the water flowing from raincloud to tap

By Lissa Fox Strohecker. Originally published in the Maui News, March 11th, 2012 as part of the Kia‘i Moku Column from the Maui Invasive Species Committee

(Miconia calvescens)

Family: Melastomataceae

Considered very invasive and is on the Hawaii State Noxious Weed List.
The Division of Forestry and Wildlife of the Hawaii Department of Land and Natural Resources has designated this species as one of Hawaii’s Most Invasive Horticultural Plants.

Description:

Large tree grows up to 50 feet tall
Large oval-shaped leaves, green on top, purple underneath, with three main midribs running from stem to leaf-tip
Native to South and Central America, introduced to Hawaii as a garden plant in 1961 and spread around by plant enthusiasts

Harm:

Forms thick stands, shades out native plants and completely takes over moist and wet forests
Forms an “umbrella” over the watershed, potentially reducing the amount of rainwater that seeps into the watershed.
Shallow root systems promote erosion
Can grow from seed to mature seeding tree in four years. A mature tree can produce about 3 million seeds several times per year. Seeds can remain viable for 10 or more years before sprouting
Sand-grained sized seeds easily spread by birds and other animals when they eat the fruit. Seeds also spread by people when contaminated dirt or mud sticks to shoes, clothing, equipment, or vehicles
Introduced to Tahiti in 1937 and has since overwhelmed two-thirds of Tahiti’s forests, and is directly responsible for threatening 25% of their native forest species with extinction

In Hawaii:

Kauai – One population known, in the Wailua State Park and Homesteads area. KISC works with partners to survey for and control all known miconia on Kauai. Land owners and tenants can allow KISC to survey their property and eradicate miconia.
Oahu – Originally introduced and traded amongst botanical gardens in the early 1960’s, miconia has since spread into several locations in the Koolau range. The potential population boundary extends to 9,500 acres (including areas considered “seed banks”). If left uncontrolled, miconia could infest up to 121,300 acres on Oahu. OISC is working to survey all population boundaries to completely eradicate it from Oahu.
Maui – Introduced to Maui in the early 1970s at a private nursery and botanical gardens near Hana. Infestations now occur in the forests near Hana, Nahiku, Keanae and Huelo. Today, approximately 37,000 acres throughout East Maui, could potentially contain miconia. Eradication is unlikely and resource managers hope to keep the species contained until an effective natural enemy can be found. Miconia is not known from West Maui.
Molokai – Miconia is not known to be present at this time. Seeds could arrive in soil on hiker’s or hunter’s shoes or gear, or on native tree fern logs imported from the Big Island. MoMISC educates community members to aid in early detection.
Lanai – None known.
Kahoolawe – None known.

For more information, see:

The Big Drip: Possible Water and Soil Impacts of the Miconia Invasion in Hawai‘i from MISC’s Kia’i i nā Moku Newsletter
All hands can be part of defense against Miconia invasion from MISC’s Kia’i Moku Column
From the Forest to the Faucet, Every Drop Counts from MISC’s Kia’i Moku Column
Invasive plants=Less water from MISC’s Kia’i Moku Column
Conservation: Helping the Economy and the Environment from MISC’s Kia’i Moku Column
Miconia calvescens information from HEAR
Miconia calvescens information from PIER
Miconia calvescens information from ISSG
KISC’s miconia survey and eradication program
MISC’s 2009 International Miconia Conference

From Paper Maps To GPS Units, The Evolution of Technology in Conservation

Posted on December 19, 2012 by MISC Leave a Comment

GPS-enabled field computers help pilots and crews record where they’ve already surveyed and where they need to go.

If smart phones, tablets, and global positioning systems (GPS) are on your wish list, you are not alone. These gadgets are proving essential in the efforts to protect native Hawaiian ecosystems.

Accurate mapping has always been crucial to surveying for and controlling invasive species. Back in the mid 1990s Maui field crews first began finding miconia. Though not very long ago, the technology available then seems pre-historic today. Using altimeters and orienting from known physical landmarks, they would record plant locations by drawing dots on photocopies of topographic maps. These paper maps were filed away for future use. Subsequent visits meant more hand-drawn maps. Sometimes the only way to find a specific locale was to bring along someone who had been there before.

Early attempts to create electronic maps involved scanning topographic maps into a computer and then drawing dots to estimate locations using computer programs intended for design and drafting. There was an electronic record, but it was time consuming to create and not especially accurate.

Then along came the GPS, promising a precise reading of position and time anywhere on earth, in any type of weather, provided the receiver had an unobstructed view of 4 satellites. Early GPS units were expensive and heavy. Accuracy was, well, not all that accurate. That unobstructed view of satellites was often hard to come by given terrain and canopy cover—especially in Maui’s dense rain forest, where miconia was spreading. To record a position, field crews carried a pole that they had to piece together and snake up through the overhanging tree limbs. With luck and patience, they could get enough satellites to provide a reading and not lose the antennae in a tangle of branches.

Rather then depending on paper maps and memory, field crews now load maps onto GPS units that allow them to record where they control plants and guide them to where they need to search.

GPS receivers have improved dramatically. Now field crews load maps onto GPS units and follow pre-recorded trails to locate remote populations of invasive plants. Rather than relying solely on the memory of a few people, crews can be dispatched to remove plants even if no one among them has visited the area before. Hand-drawn maps are a thing of the past, transforming an unwieldy stack of maps into a few digital files, making it possible to track work on hundreds of thousands of miconia plants.

Helicopters survey vast areas for invasive plants while flight lines are recorded on GPS units to ensure thorough coverage. Spotters in the aircraft record precise locations of plants so crews can revisit the locations either on the ground or by air. Each helicopter has a GPS-enabled field-rugged laptop loaded with maps to help guide the pilots and spotters.

Even flight following has changed dramatically. Pilots and crew used to have to stop what they were doing and radio in every 20 minutes to let managers know they were safe. Often, terrain blocked radio calls and pilots had to spend valuable time flying to an area where they could make contact. Now flight followers back at headquarters can monitor the helicopter’s whereabouts and status using a computer program synchronized with the GPS unit on the aircraft.

Technology has helped to increase efficiency and effectiveness of field crews on Maui and now these tools are in the hands, or pocket, of anyone with a smart phone. While plans are in the pipeline for invasive species reporting apps specific to Hawai‘i, there are many other options for reporting invasive and rare native species. If you are a cell-phone shutterbug you can easily send photos to email addresses-just type in an email where you would normally enter a phone number. You can also report online via the reportapest website at reportapest.org. So next time you see plant or animal that causes you to raise an eyebrow just snap a photo and send it in and stay posted for future tools to help you learn more about the plants and animals in your backyard.

By Lissa Fox Strohecker. Originally published in the Maui News, December 9th, 2012 as part of the Kia‘i Moku Column from the Maui Invasive Species Committee.
You can find all the articles in the Kia‘i Moku series http://www.hear.org/misc/mauinews/

The Big Drip: Possible Water and Soil Impacts of the Miconia Invasion in Hawai‘i

Posted on May 10, 2012 by MISC 1 Comment

By Thomas Giambelluca

Anecdotal evidence suggests that, besides impacting biodiversity, the invasive tree Miconia calvescens is causing landslides and other soil erosion problems in Tahiti, where it has displaced native forest. As miconia takes hold in Hawai‘i, local scientists and environmental organizations have voiced concerns about its potential hydrological impacts: increased flooding, diminished groundwater supply, loss of topsoil, and siltation of coral reefs.

Miconia invasions lead to dense, monotypic stands with little or no ground-covering vegetation. Miconia’s large, dark leaves reduce light levels beneath the canopy, thereby inhibiting the germination and growth of other plant species. Large leaves also produce relatively large throughfall drops during and after rain events.

“Throughfall” refers to rainwater that reaches the forest floor. Some throughfall consists of raindrops that fall through the forest canopy without hitting any leaves or branches. The rest comes from drops that splash or drip from wetted vegetation. Water that drips from the leaves of tree canopies can be much larger than raindrops. If falling from a great enough height, these large drops can reach kinetic energy levels that exceed that of natural rainfall in open areas. Because these large drops hit the ground with greater force, they can result in greater impacts to the soil.

The soil surface, exposed due to the lack of ground cover, is vulnerable to higher rates of “detachment,” the breakup of clumps of soil into small particles. Mobilized by large, high-energy throughfall drops, these particles can clog soil pores and reduce rates of infiltration. This leads to overland flow during rainfall events, a process unlikely to occur on undisturbed soils of native forests on Pacific Islands.

In a pilot study funded by the U.S. Fish and Wildlife Service we were able to verify that light levels under miconia stands in Onomea on Hawai‘i Island are very low.* Based on a limited survey, we also observed ground cover to be very sparse under miconia, with very little live vegetation and meager leaf litter. Most studies have shown that runoff and soil erosion become severe as ground cover declines below fifty percent, as was the case for the Onomea miconia stands.

Using laser disdrometers, Japanese researcher Dr. Kazuki Nanko helped us measure the size and velocity of throughfall drops under miconia and other tree canopies at Onomea and nearby field sites. Dr. Nanko found that miconiaproduced throughfall drops up to seven millimeters in diameter, much larger than typical two-millimeter diameter rainfall drops and significantly larger than throughfall drops under native trees.

Large miconia leaves act as umbrellas, shading out sunlight

The next step in this research is to observe runoff and erosion processes at miconia plots and control sites. Due in part to the effectiveness of miconiaeradication efforts in Hawai‘i, we have not been able to find stands large enough and in proximity to appropriate control sites to do the research in Hawai‘i. It is therefore likely that further study of hydrological impacts of miconia will be based in French Polynesia, where the miconia invasion is much more advanced.

Thus far, our studies indicate that in areas invaded by miconia, the effects of sparse ground cover, high-impact throughfall, and overland flow could combine to produce excessively high rates of soil erosion. Accelerated soil erosion removes topsoil, depriving native plants of access to nutrients and water and leading to siltation of streams and the near-shore marine environment.

Thomas Giambelluca is a professor at the University of Hawai‘i at Mānoa, where he has been conducting research on the climate and hydrology of Hawai‘i and other tropical areas for nearly 30 years.

*Dr. Ross Sutherland, professor and chair of the Geography Department at the University of Hawai‘i (UHM); Ryan Mudd, UHM graduate assistant; and Dr. Alan Ziegler, Singapore National University, contributed to this study.

Originally published in the Summer 2010 edition of the Maui Invasive Species Committee’s newsletter Kia‘i i Nā Moku o Maui Nui. The full newsletter is posted at hear.org/misc/newsletter/

All hands can be part of defense against Miconia invasion

Posted on August 5, 2011 by Lissa Strohecker Leave a Comment

: Makawao residents point to where a miconia seedling grew out of their hapu`u fern in Makawao

: Large miconia leaves act as umbrellas, shading out sunlight

In April of 2006, a Makawao resident noticed an unusual plant growing in his yard. It had large leaves with purple undersides. Curious, he did some research and discovered it was miconia – a plant native to Central and South America that is invading Maui’s rain forests. Surprised by his findings, he immediately called the Maui Invasive Species Committee (MISC). MISC staff investigated and was stunned to find a miconia seedling growing out of a hāpu‘u fern in Makawao! To date, miconia was known only from East Maui (one intentional planting in West Maui had been eradicated). Because the resident knew the origin of the hāpu‘u (Big Island), MISC surmised that a tiny miconia seed had hitched a ride on a hāpu‘u harvested from a miconia-infested area and sprouted three years later. The miconia plant was young and had not seeded, a plus for the environment. Left undetected, the plant would have quickly matured, eventually releasing ten to twenty million seeds each year into an area thought to be miconia-free.

Miconia was first introduced to Maui in the 1960’s as an ornamental plant in Hāna, then quickly spread to the surrounding forests. By 1993, one plant had multiplied into thousands, distributed over a 2,000-acre area. Alarmed by miconia’s potential to overwhelm available resources, conservation agencies pulled together and formed the Maui Invasive Species Committee (MISC), a voluntary partnership to protect Maui County from invasive plants and animals. Over the years, MISC’s focus broadened to include many other invasive species, but miconia continues to be the top priority plant target. MISC now has a full-time crew searching for and destroying miconia over thousands of acres in East Maui.

Miconia leaves can grow to be the size of a small child, averaging 2-3 ft long and 1 ft wide. The leaf has a dark purple underside, oval shape, and 3 distinct veins. In its native environment of South and Central America, miconia’s large leaves help the plant capture limited sunlight in dense, dark forests. On Maui, the forest structure has a more open canopy, so many native plants have not developed a tolerance for dense shade. Miconia’s leaves act as “light” umbrellas, casting a deep and often deadly shade over native vegetation.

A characteristic common to many invasive plants is the ability to produce large quantities of seeds that remain dormant for a long time. Miconia is no exception. Each mature plant can produce millions of seeds per year, which may not germinate for another 8–10 years. The rapid spread of miconia in East Maui has been aided by unintentional movement of these tiny seeds, as small as a grain of sand. Birds, hunters, hikers, vehicles, and even the movement of other plants, can bring miconia to new areas.

You can help combat the spread of miconia. Learn how to identify the plant. A good resource for photos and information is www.mauiisc.org. Always clean your shoes and gear before and after hiking. Know the origin of plants that you purchase. If you think you have found miconia, report the location to 573-MISC (6472). If you have miconia on your property, allow MISC to control it free of charge. Just by doing these simple preventive measures, you are helping to keep Maui nō ka ‘oi. Keep an eye out for this new monthly column to learn how you can protect Maui from invasive plants and animals that are threatening Maui County.

By Joylnn Paman
Originally published in the Maui News, August 13, 2006 as part of the Kia‘i Moku Column. Check out all of the MISC articles in the Kia`i Moku series at: www.hear.org/misc/mauinews/