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Hart Crowser Hawai‘i Office He‘eia Work Day

He‘eia Stream Estuary

The Hart Crowser Hawai‘i team working at He‘eia Stream Estuary. In the area in the right half of this photo we’ve removed the invasive knot grass. The remaining akulikuli is looking a bit trampled, but will recover quickly and thrive.

On Wednesday, June 27, the Honolulu staff each dedicated a vacation day to volunteer with Hui Ko‘olaupoko (HOK) at He‘eia, O‘ahu. HOK is a non-profit watershed management group established in 2007 to work with communities to improve water quality through ecosystem restoration and storm water management, focusing specifically in the Ko‘olaupoko region on windward O‘ahu. HOK’s mission is to protect ocean health by restoring the ‘āina: mauka to makai (land: mountain to sea).

HOK implements innovative projects that effectively manage and protect water quality and natural resources. Projects have included storm water low-impact development projects such as rain gardens, and other watershed focused projects.

The He‘eia estuary restoration project is a collaboration with several other non-profits to restore the ecosystem of He‘eia Stream. This project is aimed at improving water quality and increasing habitat for native aquatic animal species by removing invasive plants and replanting native Hawaiian species. In the past 3 years, about 4 acres of mangrove have been cleared and native species planted. Our work for the day consisted of removing invasive “knot grass” from the estuary flats where it was overwhelming the native vegetation that was planted following removal of the mangrove.

For the plant nerds among us, the predominant native vegetation we protected in the estuary flats were:

  • Akulikuli (Sesuvium portulacastrum), an indigenous coastal succulent ground cover that has been very successful in the estuary
  • Mau‘u‘aki‘aki (Fimbristylis cymosa), a sedge that forms short, rounded tufts of light green narrow, stiff, erect blades
  • Ahuawa (Mariscus javanicus), a greenish blue rush with beautiful brown spiky umbrella flowers/seed pods

We also got to see many native and rare species that have been planted along the stream bank, including Ilima with its tiny flowers that need about 500 to make a lei!); Lama; Ohai; and Mao hau hele. All of these plants have interesting cultural uses and significance, well explained at these website links by our friends at Hui Kū Maoli Ola, an amazing native plant nursery in upper He‘eia.

One of the delights of working on this project was getting to visit the adjacent He‘eia Fishpond. Paepae o Heeia, another non-profit, has been restoring the 88-acre, 800-year-old fishpond since 2001. He’eia Fishpond was likely constructed by hundreds, if not thousands, of Hawaiians who passed and stacked rocks and coral for approximately 2-3 years to complete the 1.3-mile wall. Fishponds helped Hawaiians practice sustainable aquaculture long before western contact. There are only a few fishponds remaining of the approximately 100 that are known to have existed on O‘ahu, as most have been destroyed by development. Restoration of remaining fishponds has been a big part of the Hawaiian cultural renaissance over the past 25 years. While we didn’t work on the fishpond itself, we were able to cross the stream to walk on the fishpond walls (which are dry stacked!), to view the functioning sluice gates, and to learn more about fishponds.

We had a fun team-building day that successfully cleared invasive species from a large area, and learned a bit more about native plants and Hawaiian culture around fishponds. Thanks to HOK for hosting us, and kudos to our Hawai‘i team for being adventurous and volunteering their own time to take on this project!

Ko‘olau mountains

The beautiful Ko‘olau mountains in the distant background, a portion of the fishpond wall and sluice hale in the midground, and our team working hard in the foreground.

Walking on Fishpond Wall

Walking on the fishpond wall after a long day of work; the enclosed fishpond is to the left, with the open waters of Kāne‘ohe Bay to the right.

Hawaii team

Our Hawaii team is all smiles visiting He‘eia Fishpond after a long day of work helping to restore He‘eia Estuary.

Sluice gates

The working mākāhā (sluice gates) of He‘eia Fishpond.

Ilima,official flower of O‘ahu

The beautiful native Ilima, the official flower of O‘ahu. The little flowers are treasured for lei – it takes more than 500 of these flowers to make a delicate and special lei.

 

Invasions are not just military (Part 2)

 

Butterfly Bush

Butterfly bushes displace native vegetation and in spite of the name, negatively affect native butterflies. We didn’t have to go far to take this photo.

In a previous post about invasive species, we learned what invasion meant and who the invaders look like. Now let’s discuss how invasive species get a foot hold in the first place and what can be done about it.

How Invasions Happen

Invasive species can be introduced intentionally or unintentionally. They may be introduced intentionally to benefit the ecosystem by restoring habitat, increasing fish stock, or controlling pests. Unintentionally, they:

  • Are released in ship ballast;
  • Escape from fish farms;
  • Are used in recreational activities;
  • Are used as live bait;
  • Arrive through canals;
  • Are released/escape from aquariums;
  • Are used in unauthorized fish stocking; and
  • Can be introduced by many other means.

In order to successfully invade a new environment, certain biological characteristics are necessary. Many invasive species have high reproduction rates, short generations, long life, high dispersal rates, broad native range, and broad diet. However, not all species immediately survive in new environments. They can fail multiple times before flourishing. Invasion success is context dependent.

Controlling the Invasion

Strategies to control invasive species include (1) keeping potential invaders out, (2) eradicating potential invaders soon after invasion, (3) biological control, (4) chemical control, and (5) mechanical control.

Keeping potential invaders out

Keeping potentially damaging invaders out in the first place is the most cost-effective method. The danger can be reduced by monitoring the common invasion pathways such as ship ballast water, wooden packing material, and horticultural plants.

 Eradicating after Invasion

It is easier to eradicate invasive species if they are discovered quickly and population levels remain low. Even if it proves impossible to totally eliminate an invader, early intervention can keep the population at acceptably low levels. For example, Giant African Snails were effectively eliminated from Florida. Currently researchers in California are attempting to eradicate the marine green alga Caulerpa, a recent invader.

Biological Control

Biological control involves introducing an enemy of an invasive plant (for example, a disease, parasite, predator, or competitor) in an attempt to lower invader population size.

Sometimes introducing a natural enemy from the native range of the introduced pest can be effective. For example, prickly pear cactus, which invaded Australia from the Americas, has been effectively controlled by introducing a moth from South America whose caterpillar feeds on the cactus. In other cases finding an enemy from a different area (a novel association) works because the invader may not have evolved defenses to a species with which it has never been in contact. For example, a virus from South America has been used to control European Rabbits in Australia.

A disadvantage of biological control is that some agents attack nontarget species, becoming noxious invaders themselves, and it is very difficult to remove a troublesome introduced natural enemy once it is established.

Chemical Control

Although chemical pesticides can effectively control some species (for example, water hyacinth in Florida), it can have problems. Pesticides may affect non target species, can be expensive, and may only be effective for a limited time if pests evolve resistance.

Mechanical Control

Mechanical control involves using machinery or human effort to remove invaders, often manually. Mechanical control has been an effective control strategy for invasive Tamarix (arid climate adapted shrub) in the Southwestern United States. Volunteer convict labor has been used in Florida to cut paperbark trees and in Kentucky to rip out Eurasian musk thistle.

Ecosystem Management

The newest technology for managing invaders is ecosystem management, in which the entire ecosystem is subject to a regular treatment (such as a simulated natural fire regime) that tends to favor adapted native species over most exotic invaders. Because it is so new, the specific ways in which ecosystem management can be employed must be determined in each type of habitat.

Want to learn more?

Invasive species are everyone’s problem. Learn more about what you can do to help prevent them:

Washington Invasive Species Council

Washington Department of Fish and Wildlife Aquatic Invasive Species

US Department of Agriculture, Invasive Species State by State

Invasions Are Not Just Military

Atlantic Salmon

Atlantic Salmon. Photo: Maine Atlantic Salmon Commission

One of the most destructive forces on an ecosystem is a non-native species with no natural predators or other natural controls. These species can overtake their new home in an extraordinarily short period of time by multiplying, consuming prey, and colonizing, crowding out essential local species.

An invasive species is an organism (plant, animal, fungus, or microbe) that is not only foreign to a specific area or habitat but also has negative effects on its new environment and, eventually, on our economy, our environment, or our health. Not all introduced species are invasive; the distinction is how aggressively they interact with their new surroundings.

Why we Care

Invasive species are the second greatest threat to biodiversity (the first is habitat loss). Almost half of the species at risk of extinction in the United States are endangered directly due to the introduction of non-native species alone, or because of its impact combined with other processes. In fact, introduced species are considered a greater threat to native biodiversity than pollution, harvest, and disease combined. They threaten biodiversity by (1) causing disease, (2) acting as predators or parasites, (3) acting as competitors, (4) altering habitat, or (5) hybridizing with local species.

Invasive species are costly to both society and nature by:

  • Costing Americans more than $137 billion a year (Pimentel et al. 2000)
  • Impacting nearly half the species listed as threatened or endangered
  • Possibly devastating key industries including seafood, agriculture, timber, hydro-electricity, and recreation
  • Impeding recreation such as boating, fishing, hunting, gardening, and hiking
  • Spreading easily by wind, water, animals, people, equipment, and imported goods
  • Increasing the frequency of localized wildfires and adversely affect watering availability
  • Destabilizing soil and alter hydrology of streams, rivers, lakes, and wetlands

Washington State Invasive Species Examples

There are over 50 priority invasive species of concern in Washington State. Here are a few examples that threaten Western Washington.

Atlantic Salmon

Atlantic salmon (many genetically modified) are raised along the Washington and British Columbia coasts; escapes from these aquaculture operations concern fishery biologists and others working to restore native Pacific Northwest salmon runs. As of 2006, the Aquatic Nuisance Species Project states that there have been sightings of juvenile Atlantic salmon on the West Coast. The last reported sightings were on Vancouver Island in 2000.

In recent years there has been specific concern about the potential impact on wild salmon stocks from sea lice (Lepeophtheirus sp.), originating from net pens of Atlantic salmon in British Columbia. Sea lice can kill juvenile fish, even at low infestation levels.

Spartina

Spartina

Spartina flowering in estuary
Photo: Washington State Magazine

Spartina species are aquatic grasses that grow on the mud flats and marshes of Puget Sound and our coastal estuaries. The plants tend to grow in circular clumps called ‘clones’ and are bright green. One particular species, Spartina anglica, was introduced either in shipments of oysters from the East Coast or as packing material in ships’ cargo. It creates large monocultures that outcompete native plant species for space, including rare and endangered plant species, reducing marsh biodiversity and ecological functions.

European Green Crab

European green crab

Juvenile green crab began showing up in Washington waters in 1998. Photo: Washington State Department of Fish and Wildlife

The European green crab is a small shore crab that is not necessarily green like its name implies. It typically is found in high intertidal areas and marshes in coastal estuaries and wave-protected embayments, and can live on a variety of surfaces including sand, mudflats, shells, cobble, algae, and rock. It is an opportunistic feeder and aggressive invader. It is native to the eastern Atlantic from Norway to North Africa.

The European green crab is a ravenous predator that eats small crustaceans and many other plants and animals, and can have dramatic negative impacts to native shore crab, clam, and oyster populations. First introduced to the East Coast of the US, green crabs are believed to have caused the collapse of the soft-shell clam industry in New England; their digging habits also have slowed eelgrass restoration efforts. One green crab can consume 40 half-inch clams a day, as well as other crabs its own size. On the West Coast, green crabs were introduced to San Francisco Bay either via ballast water or through the lobster trade. Further invasion north is facilitated by strong advective currents that are associated with El Nino events. The 1998 event brought crabs as far north as Vancouver Island; luckily populations have not established yet. This year’s El Nino may prove strong enough to bring crab larvae into Puget Sound and British Columbia again. How severe the invasion will be, only time will tell.

Scotch Broom

Scotch Broom

A member of the pea family, Scotch Broom has pretty flowers but an aggressive demeanor. Photo: King County

Scotch broom (Cytisus scoparius) is an upright shrub with yellow flowers in the pea family. It grows primarily in open, dry meadows and along roads. It is an aggressive early colonizer and typically shows up in recently disturbed areas. A European native, scotch broom crowds out native species and negatively impacts wildlife habitat by creating vast monocultures. It can form dense, impenetrable stands that displace farmland and/or prevent native species from colonizing. Scotch broom also produces toxic compounds, which in large amounts can cause mild poisoning in animals such as horses.

Coming up: in Part II, we will discuss how invasions happen and what can be done to stop them.

For more information, contact Jason Stutes at jason.stutes@hartcrowser.com.

References: Pimentel, D., Lach, L., Zuniga, R., Morrison, D., 2000. Environmental and economic costs associated with non-indigenous species in the United States. BioScience 50 (1), 53–65.