The landscape changed forever soon after the arrival of the first permanent residents in 1902. Over 200 plant species were introduced, including many ornamental plants and crops that were brought to Midway during the earliest years of the Commercial Pacific Cable Company. Most now have a localized distribution at Midway, but some have become serious management problems, having spread across the islands virtually unabated.

The dominant tree on the island is ironwood (Casuarina equisetifolia). It grows in dense, monotypic stands. Ironwood trees can grow as much as 40 feet in an 18 month period and they rapidly invade open areas in the absence of aggressive management. The ironwood root systems take up most of the soil nutrients which, together with the thick mulch of fallen branchlets, prevents the growth of other plants. Golden crown-beard (Verbesina encelioides) is another management headache for Midway refuge staff. Golden crown-beard is a yellow flowered annual shrub which grows rapidly and in such dense stands that it can exclude nesting birds from otherwise desirable habitat.

The vast majority of species that make up Midway's insect fauna have also been introduced to these islands, some intentionally and others accidentally. Many surely arrived in the 9,000+ tons of soil that were imported to Midway in the first third of the last century for ornamental and agricultural purposes. Others have arrived as unwanted guests on boats, planes, and the soles of people's shoes.

The introduced species with the most profound effect on Midway's native wildlife is almost certainly the Black rat (Rattus rattus). For decades, the rat population proliferated on Midway, virtually unchecked. The result has been the extirpation of nesting Bulwer's petrels and sharp declines on breeding productivity of Bonin petrels and Wedge-tailed shearwaters. A very aggressive rat control program, began in the mid 1990s, and was successful in eradicating rats from the entire atoll. The positive effect on Bonin petrel nesting success is already evident. Mice are still found on Sand Island, but do not appear to cause significant, negative impacts on seabirds.

Midway is also home for two bird species that appear to have adapted well to island life. Common canaries(Serinus carius) were introduced soon after the first inhabitants of the Commercial Pacific Cable Company arrived at Sand Island. They are well established in small flocks that can be seen island wide. Even more conspicuous is Midway's population of Common Mynas (Acridotheres tristis), a bird that is widespread throughout the main Hawaiian Islands.

Photos of Non-native Reptiles on Midway Atoll NWR.