Nonnative Species

Lopa trees.

NPS photo.

What is an Invasive Species?

An invasive species is any living organism that is not native to an ecosystem and causes harm. These species grow, reproduce rapidly, and spread aggressively, often outcompeting native species and disrupting the environment.

The Lopa Tree (Adenanthera pavonina)

The Lopa tree, native to South Asia and Malaya, was introduced to American Samoa and has since spread widely across the islands. Samoans use Lopa seeds for a variety of purposes, including jewelry, weighing, and firewood. Despite its uses, the Lopa tree is classified as an agricultural weed in the Global Compendium of Weeds due to its rapid growth and aggressive spread. It forms dense thickets that compete with and displace native vegetation. Like other invasive species, the Lopa tree poses a threat to native ecosystems and is considered one of the worst invasive species in countries like Jamaica, Australia, and across the Pacific islands.

 

Seed pods growing on a tree.

NPS

How Does the Lopa Tree Harm Our Native Trees and Environment?

The Lopa tree is a prolific seeder, meaning it can produce and disperse large quantities of seeds, which outcompete native plants for space and resources. Lopa trees are also nitrogen-fixing, which can alter the soil composition and reduce its productivity. Similar to the invasive Tamaligi tree, Lopa seeds can remain dormant in the soil for long periods. When the ground is disturbed by natural disasters or human activity, these seeds can sprout, leading to the growth of new Lopa trees. Over time, this depletes the productivity of the soil and impacts native forests.

Why Should You Care?

Native forests in American Samoa provide critical habitats for native birds and other wildlife. The spread of invasive species like the Lopa tree threatens these ecosystems by displacing native plants that serve as food and shelter for wildlife. Invasive species negatively impact ecosystems, biodiversity, recreation, health, and the local economy. If native plants are lost, so are the native birds and the overall health of the island’s biodiversity.

How Can You Help?

Here are six steps you can take to help control the spread of invasive species like the Lopa tree:

1. Learn to identify native trees versus non-native trees.
2. Understand why invasive trees are harmful to the ecosystem.
3. Stop replanting invasive trees.
4. Remove invasive species like the Lopa and Tamaligi trees from your property or community.
5. Promote the planting of native plants to support biodiversity.
6. Spread awareness by sharing this information with your family and friends.

Managing and controlling invasive species has proven effective in allowing native species to regenerate and improving the island’s biodiversity. Once invasive species like the Lopa tree are removed, native trees can once again access sunlight and recover quickly, helping to block the regrowth of invasive species.

Additional Information

For more information, contact the NPSA Office:

• Phone: [phone]
• Terrestrial (ext): 50 & 52
• Interpretation & Education (ext): 20, 21 & 22