Plants

Polauta Ridge

NPS

Tropical Rainforest

The plant communities of the park, stretching from the mountaintops to the ocean, are predominantly tropical rainforests. These rainforests represent the climax vegetation of the equatorial climate, meaning they are the mature and stable form of vegetation in this environment. Unlike the temperate forests of North America, which are often dominated by just one or a few tree species, tropical rainforests are marked by their incredibly high species diversity, with many species co-dominating the ecosystem.

Because Samoa is a young oceanic island with no historical land connection to continental land masses, the native plant species arrived by chance dispersal. As a result, the species diversity in Samoa is less than in regions like Southeast Asia, which is the primary source of many plant dispersals to the island. However, the rainforest here remains incredibly important for maintaining the island’s delicate balance of life.

The Importance of the Rainforest Ecosystem

Tropical rainforests are critical for maintaining biodiversity, climate regulation, and supporting local wildlife. The dense canopy of trees provides essential habitat for a variety of species, including birds, mammals, and insects. These forests also play a crucial role in the island's water cycle, capturing rainfall, preventing soil erosion, and maintaining the flow of clean water to streams and rivers.

Rainforests act as natural barriers, protecting the land from the effects of heavy rainfall, such as landslides and flooding. Their dense root systems help stabilize the soil, reducing the likelihood of erosion. Additionally, tropical rainforests serve as carbon sinks, helping to mitigate the effects of global climate change by absorbing carbon dioxide from the atmosphere.

Flora and Fauna

The rainforest in American Samoa is home to a range of unique plant and animal species. The flora includes towering trees like the native Pometia (Tava), as well as ferns, vines, and epiphytes that thrive in the humid, warm environment. Some plants, such as the native pandanus and Falealupo trees, are important both ecologically and culturally, providing materials for traditional Samoan crafts and construction.

The fauna of the rainforest is equally diverse. The park is home to native birds such as the Samoan Starling and the rare Tooth-billed Pigeon (Manumea), which can only be found in Samoa. Many of these species rely on the rainforest for shelter and food, and the loss of this habitat could threaten their survival.

Conservation Challenges

Despite its resilience, the tropical rainforest faces significant threats. Invasive species, such as the Tamaligi and Lopatrees, outcompete native species for resources, altering the ecosystem’s balance. Once these invasive plants establish themselves, they form dense thickets that crowd out native vegetation and reduce biodiversity. Additionally, the impacts of climate change, including rising temperatures and shifting weather patterns, are placing additional stress on the rainforest, particularly its coral reef systems, which are vital to the island's marine biodiversity.

Human activity is another challenge. With the growing population on the island, pressure on the land is increasing. Subsistence farming, land clearing for agriculture, and development all contribute to habitat loss and fragmentation, further threatening the rainforest's ability to thrive.

Park staff, in collaboration with local communities, are working to control the spread of invasive species and promote sustainable land use practices. Ongoing research and monitoring efforts are also crucial to understanding how best to protect these rainforests in the long term.

Cultural Importance

For the people of Samoa, the tropical rainforest is not just an ecosystem—it is an integral part of their cultural identity and way of life. Many of the plants found in the rainforest have traditional uses, from medicinal plants to those used in weaving, house building, and boat construction. The pandanus tree, for example, is used to make fine mats and baskets, while the Tava tree provides materials for canoes and tools.

The relationship between Samoans and their environment is guided by traditional knowledge that has been passed down through generations. This knowledge includes sustainable harvesting practices and a deep respect for the natural world. As the park works to preserve its ecosystems, it also seeks to support the continuation of these traditional practices by involving local communities in conservation efforts.

How You Can Help

Preserving the rainforest requires the efforts of both park staff and the local community. You can help by:

1. Learning to identify native and invasive species: Understanding the difference is key to knowing which species to protect and which to control.
2. Understanding why invasive species are harmful: Awareness helps prevent the spread of invasive species through replanting or land use practices.
3. Avoiding replanting invasive trees: When planting, choose native species that support the ecosystem.
4. Removing invasive plants: Help control the spread of invasive species like Tamaligi and Lopa.
5. Promoting native plants: Encourage the growth of native plants to support the health of the rainforest.
6. Spreading the word: Educate friends, family, and your community about the importance of protecting the rainforest.

Working Together

The tropical rainforest in American Samoa is an incredible example of nature’s complexity and beauty. Protecting it is essential not only for the plants and animals that call it home but also for the people of Samoa who rely on it for food, materials, and cultural identity. By working together to control invasive species, reduce human impacts, and promote sustainable practices, we can ensure that this rainforest continues to thrive for generations to come.

Related Information

• Technical Report – Plants of Tau
• Technical Report – Plants of Tutuila and Ofu
• Rare Plants of American Samoa
• Inventory & Monitoring Program – Pacific Island Network

Learn More: Plant Inventory.