Place to Protect: How Invasive Species Modify Ecosystems | News, sports, jobs
We are surrounded by relationships — with family members, friends, familiar faces and acquaintances. People we know at work, school, and church. We are shaped and shaped by all the interactions in our lives, including our surroundings. Each of us is part of an ecosystem of relationships – one that has grown and evolved since the first breath we took.
Tansley’s terminology stuck, but the concept was not new. For thousands of years, humans have observed and studied the relationships and interactions in their surroundings. Komolepo, the Hawaiian hymn to creation, emphasizes the interconnectedness of the earth, sky, oceans, plants, animals, and humans. So do ancestral narratives from cultures around the world. Like our origin stories, there is a beginning—the first arrival, from which all relationships flow. In Hawaii, connections have been forged over thousands of years, with new species successfully establishing themselves once every few thousand years, finding or creating new niches within the larger fabric. The frequency of arrivals has increased over the past hundreds of years, increasing the potential for damage to the system. When a plant, animal or microorganism is invasive, it can have a disruptive and destructive impact on the ecosystem.
Soils in Hawaii are naturally low in nitrogen. The ability to grow in nutrient-poor soil helped ancestral plants colonize the islands, slowly creating forests of bare lava. The invasive Albizia tree increases nitrogen in the soil, modifying the ecosystem in a way that better suits non-native plants. Unfortunately, excess nitrogen stunts the roots of some native plants, throwing them out of balance. Invasive plants disrupt other relationships, with ripple effects throughout the ecosystem.
Invasive weeds are ecosystem modifiers. Soil moisture is affected by these invasive weeds, as is the composition of microbes and nutrients that affect the growth of other plants. Grasses are often drought tolerant, and can grow rapidly over a few months. The leaves die back, but they do not decompose, and can accumulate biomass over the years. In Hawaii, invasive grasses reduce the growth of native plants and shrubs, shifting the plant community toward more grasses. The accumulation of dry, dead leaves creates a mass of fuel ready to burn.
Native plants that survive fires in Hawaii often do not recover because they are not adapted to the fire cycle. Fire does not play a significant ecological role in Hawaii because there are few historical sources of ignition (other than lava flows). In contrast, many of the non-native grasses here are shaped by a long history of fires and lightning-triggered disturbances. They quickly recolonize the burn scar with abundant seeds or sprout from deep underground roots. The grasses have turned an ecosystem where fires are rare into a fire-prone one, waiting for a spark.
These altered ecosystems do not return to native plants, even after years without fire. Researchers who examined sites on Hawaii Island found that the area that had burned twice was already beyond the threshold for natural recovery, even 20 years after the fires were extinguished. Plants found at these historic burn sites included invasive woody grasses and shrubs.
Like the individual relationships we build during our time on this planet, most of them are positive — or, at worst, annoying. Most non-native plants are desirable for their food or beauty, and either adapt well to the rest of the population or can be kept in check through regular maintenance. But some of them are simply not compatible. Local flora and fauna cannot uproot it and move to another location. Without vigilance, more disruptors will arrive, establishing and forever changing the ecosystems we call home.
Sir Arthur Tansley and his peers don’t always include people as part of the ecosystem. Komulipo emphasizes Kanaka’s place in the ecosystem. People are not separate from the environment; We are from him. Our relationships are as intertwined with place, plants, and animals as they are with each other.
*Lisa Strohecker is the public relations and education specialist for the Maui Invasive Species Commission. She holds a degree in biological sciences from Montana State University. kiay moko, “Guarding the island.” It was prepared by the Maui Invasive Species Committee to provide information about protecting the island from invasive plants and animals that could threaten the island’s ecology, economy, and quality of life.
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