Jarvis Island, part of the Line Islands, is an island about 2 square miles, located 1200 miles south of the island of Hawaii, a half a degree into the Southern Hemisphere. The closest inhabited land is Kirismati, part of Kiribati, 200 miles to the northeast. The island is the top of a long-extinct volcano. It was originally settled, and claimed, by the United States of America during the guano-mining phase of the 1800s. Unlike many other such territorial acquisition, this was free of colonialism, since the island was uninhabited by any indigenous population. While Polynesian sailors might have known about the island, they never settled on it. It has no source of water, only occasional rain, and its vegetation consists only of shrubs and grasses. Unlike other Pacific Islands, it doesn't have even a rudimentary airstrip.
It is very hard to find information about, and photographs of Jarvis Island. Google Maps has over a 100 reviews of it, all jokes. Even Navassa Island is Grand Central Station in terms of number of visitors and documentation compared to Jarvis Island. The best information about Jarvis Island comes from the US Department of Fish and Wildlife.
Because what is terrible habitat for humans is great habitat for birds. And the waters around Jarvis Island are great habitat for sea life. So while the barely vegetated, remote island hosts no trees or mammals, it is a nesting ground for "up to one million Terns". The only other vertebrate life is a single species of lizard. It is home to a great number of hermit crabs, and the waters offshore are the center of a great reef ecosystem. The exact components of the land and ocean ecosystems are not well-studied, because even the Fish and Wildlife Service only "visit Jarvis about every 2 to 3 years".
Even among the far-flung and remote Pacific Islands, Jarvis is one of the most remote.
https://www.fws.gov/refuge/Jarvis_Island/about.html