conservation & education
How did species get to Hawaiʻi?
Millions of years ago, long before humans, the Hawaiian Islands were formed from magma spewing up from a hotspot in the ocean floor. Born of fire and water, Hawaiʻi’s incredible diversity had to come from somewhere. Over the course of millenia, various land and aquatic beings slowly colonized the islands, transforming them from barren rock to lush habitats we know today. Fish and corals made their way on ocean currents from the Indo-Pacific, while plants and animals arrived from water and air. Once here, many quickly evolved into new species to make better use of the open habitats.
While all Hawaiian species arrived here from somewhere else, some of the new arrivals are considered invasive (introduced and cause ecological damage). The natural progression of species colonizing islands is generally a slow process, but with global interconnected shipping and travel, humans have been facilitating the spread of invasive species at an unprecedented rate. The ability for invasive species to out-compete natives are among the greatest threats to tropical biodiversity, and can cause the extinction of endemic species (those existing only in one place). A big problem with a lot of introduced species to Hawaiʻi is they thrive because their natural predators or pests that compete with these species are not present in this new environment. There are many invasive species present in Hawai’i, and they all got here under different circumstances. Some traveled here in voyaging canoes, long before western contact (e.g. pigs). Some were introduced as scientific experiments, with researchers thinking they would help to control other species that were getting out of hand (e.g. mongoose to combat rats). Some species arrived by accident, as stowaways on marine debris or as a consequence of emptying ship ballast water (e.g. prickly seaweed). Some species were shipped here just because they were pretty, or as gifts to royalty (e.g. ornamental grasses).
Invasive & Native Plants in Hawai'i
the threat of invasive plants
Depending on where you are in Hawaiʻi, it can be difficult to pick out native species because of the recent dominance of invasive flora. Many hikes are quite popular due to their invasive species of plants. For example, bamboo forests might seem tropical and scenic, but they are quite damaging and proliferate rapidly. On the other hand, invasive marine plants (algae) are creating barren wasteland reefs, which impacts overall diversity and functioning of coral reefs. While mangrove trees are protected in most parts of the world, here in Hawaiʻi they were introduced and actually have a negative impact on native wetlands by trapping sediment and re-engineering coastal habitats.
One of Hawaii’s most magical endemic trees, the ʻŌhiʻa lehua, is also in trouble. This plant is special because it is one of the first plants to appear after a fresh lava flow in primary succession (creating suitable habitat for later species). They also make up 80% of native forests, particularly at altitude. However, rapid ohia death (ROD), a fungal disease, has been wiping out this endemic plant. Scientists aren't sure yet where this disease is coming from and it’s important to do all that we can to take care of this endemic species.
One of the most magnificent trees in Hawaiʻi for travelers to see is the giant Albizia, which is a beautiful tree that creates a massive canopy. Albizia are insanely quick growers, and shade out competing endemic species below. Their ability to grow fast means that they sacrifice structural stability. They have become known as ‘widow-makers’ due to their massive limbs collapsing on unsuspecting people below. If you are ever in Mānoa valley, it is infested with beautiful Albizias– which gives you the idea of how invasive they really are.
Endemic Plants of Hawai'i
native ohia
only found in hawai'i & threatned by rapid ohia death
What you can do to stop the spread of invasive plants
The spread of ROD is why it is important to wipe off or clean your hiking boots before starting any hike. There are usually shoe scrapers at the beginning of hikes, which reduces the spread of invasive plant seeds and limits ROD spread. Rubbing alcohol can also be used to sterilize the soles of hiking footwear and prevent the spread of plant diseases. It is important to clean your hiking gear prior to adventuring in a new area.
A huge way to offset the invasive species vs endemic species composition is joining collectives to plant native trees, or donate to conservation groups actively removing invasive species. The Hawaiian Legacy project is actively selling trees for you to buy and plant, as your tree. Their four choices are four endemic trees to Hawaii that need a higher species composition around the islands, including: king koa, ʻŌhiʻa lehua, royal sandalwood, and monarch milo. Learn more about the legacy forest initiative here.
Some botanical gardens, arboretums, and local non-profits around the island hold initiatives to remove invasive plants, and nurture endangered species (those threatened with extinction). Want to get your hands dirty and help actually remove invasive algae from impacted reefs? Mālama Maunalua is one organization where you can spend a day aiding the removal of invasive algae in Maunalua Bay on Oʻahu. Paepae o Heʻeia is another where you can help remove invasive mangroves from a traditional Hawaiian fishpond and wetland. Donating to local organizations helps restoration efforts and helps the endemic species populations around Hawaiʻi.
Here are a few others (of many):
▷ National Tropical Botanical Garden
▷ Lyon Arboretum
▷ Big Island Invasive Species Council
'ie'ie (Freycinetia Arborea)
endemic to the hawaiian islands
native tree fern
threatned by other non-native forest plants.
removal efforts are targeted by DLNR to help restore native ecosystems.
The Threat of Invasive Animals in Hawai'i
You can't visit Hawai'i without noticing the impact of the feral cat and chicken presence on the islands. The cats are predators of native birds and insects (many of which are only found in Hawai'i), and with their high populations present on the island, they have caused a decline in native species. These cats can also carry a parasite (Toxoplasma gondii) that ends up in the waterways through feces and is the greatest killer of native Hawaiian monk seals. Toxoplasmosis is also dangerous to pregnant women, and those with weak immune systems.
Chickens are omnipresent around the island. They also carry infectious diseases and are generally considered pests. The islands have started different initiatives of taking care of the population numbers of chickens as they have overwhelmed some local ecosystems in recent years.
The Jackson’s Chameleon is also an invasive species on the islands. These were brought here in the 1970’s as pets. However after escaping or being released, they exploded in numbers. The chameleons are a large predator of the Oʻahu tree snail, which is now highly endangered and only has a few species left. Most of these snails are kept in a lab at UH Mānoa or the Bishop Museum, to help conserve and repopulate these species. Jackson’s Chameleons can be found most of the time at high altitudes on hikes.
Mongoose were introduced to the islands in the 1800s to help control the rat population here. What researchers overlooked was that rats are nocturnal (only active at night), while mongoose are diurnal (only active during the day). Therefore, even though rodents are a part of the mongoose diet, they rarely interact. Worse yet, now both are still preying on native insects and birds. Biocontrol is a huge concept in the science community that has the potential to be successful, however without the right data collection and trials it can be highly detrimental instead of helpful. Today there is still an abundance of both rats and mongoose across all the Hawaiian Islands.
While cats may be cute and cuddly, they’re actually a dangerous threat to native animal species in hawai'i.
Protecting Endemic Animals
There are multiple initiatives around the island that help neuter and spay feral cats. Donating to the local humane society will help them fund initiatives to help feral cats around the islands. It is also extremely important to not feed feral animals and further exacerbate their negative impacts on native fauna.
While hiking, if you ever come across an animal exclusion fence, be sure to close the gate securely behind you. Fences are oftentimes built to specifically deter feral pigs, goats, and other pests. These simple tasks can go a long way to aid restoration efforts in fragile habitats.
If you see a chameleon, the Department of Land and Natural Resources (DLNR) suggests you take it with you and remove it from the environment. These can be pets, or better yet, they can also be turned into DLNR to ensure they do not re-enter the environment. Importing certain animals, like snakes, is illegal and any invasive pest can be reported by visiting 643pest.org.
How to minimize the affects of invasive species
control and managment
Prevention
Control and management: Established invasive species can be difficult to remove, but control and management efforts can help to minimize their impact. This may involve physical removal, chemical control, or a combination of methods. Volunteering with organizations that specialize in invasive species removal is a simple way to help out.
One of the most effective ways to combat invasive species is to prevent new introductions by controlling the import and movement of plant and animal species. This can be done through regulations and enforcement at ports of entry, as well as through public education and outreach. Taking small steps, such as cleaning your hiking boots between trails can go a long way in reducing the spread of invasives.
restoration
Restoration: In some cases, it may be possible to restore damaged ecosystems by removing invasive species and replanting native species. Restoration can help shift the balance of the ecosystem back towards native species.
early detection and rapid response
If a new invasive species is detected, rapid response is crucial in order to minimize its impact. Read more about the research being pioneered by us here (LINK to blog). Not sure what you saw? If you can snap a photo, upload it to iNaturalist.org for identification and to aid scientists with presence-absence data!
ongoing monitering
Ongoing monitoring is important to ensure that invasive species do not become re-established and to detect new introductions. This may involve regular surveys and monitoring programs, as well as citizen science initiatives that engage local communities in monitoring efforts.
