Introduced and invasive plant species have contributed to habitat degradation and the loss of suitable native forest bird habitat across Hawaii. Invasive species are non-native or alien species (plant, animal, or microbe) transported by humans to a location outside its native range and whose introduction does or is likely to cause economic or environmental harm or harm to human health (U.S. Presidential Executive Order 13112). Non-native species make their way to Hawaii every day through imported plants, people, and ships.
Invasive plants create dense growths and crowd out native plant growth, which decreases biological diversity. Additionally, many of these invasive plants use more water than native plants, thus decreasing the availability of water within the forest and the watershed. Most native birds will not feed off of non-native plants as they are not adapted to recognize them as a food source. There are organizations on island like the Maui Invasive Species Committee whose mission is to prevent invasive species from becoming established and limiting the most harmful ones.
MFBRP works in some of the most pristine areas of Maui, where much of the forest is native. Some of the top invasive plants of concern in The Nature Conservancy’s (TNC) Waikamoi Preserve include: Gorse (Ulex europaeus), Kahili Ginger (Hedychium gardnerianum), Blackberry (Rubus argutus), Pines (Pinus spp.), Blackwood Acacia (Acacia melanoylon), Tropical Ash (Fraxinus uhdei), and Eucalyptus (Eucalyptus spp.). At Nakula Natural Area Reserve, where MFBRP also works on forest restoration, there are many invasive plants such as Kikuyu grass (Pennisetum clandestinum), Velvet grass (Holcus lanatus), and Tree Poppy (Bocconia frutescens). We are also on the lookout for Koster’s Curse (Clidemia hirta), Gorse (Ulex europaeus), and Australian Tree Fern (Cyathea cooperi). Introduction of non-native plants to these areas could be caused by humans, pigs, or bird dispersal.
To prevent the introduction and spread of weed species, MFBRP takes precautions by making sure all gear is clean before entering any field sites- this includes cleaning clothing, backpacks, tents, boots, and raingear. Before each field trip, all gear is thoroughly inspected and cleaned. All dirt, seeds, and insects are carefully removed. Project field gear is never taken off island or into other less pristine areas of Maui. MFBRP also uses GPS to mark locations of non-native plants and may remove them to limit and prevent their spread. In Waikamoi, TNC is also notified of invasive plants as they have an intensive invasive species management program. Control efforts are focused on ecosystem modifying species and incipient populations that can be controlled through minimal effort. Non-native plants in camp areas, landing zones, main trails, and along fence lines are also a high priority for control in order to prevent their spread into more remote areas. Because invasive plants are often very difficult to control once they have entered an area, prevention of new introductions is crucial.
You can do your part by becoming aware of invasive plants (Hawaii’s High Profile Invasive Species List) and making sure not to spread them. Clean your camping gear and do not support more introductions. For more reading go to: Protect Hawaii-10 Ways to Help Stop the Silent Invasion.