They have cool oceanic climates with temperatures ranging from 13 °C (55 °F) in August to 17 °C (63 °F) in February, rainfall of 1,100 mm (43 in), persistent westerly winds, and high humidity levels.

Plant life changes with elevation; at lower levels the volcanoes are covered with grass and tussock grasslands and sedge meadows and, on Amsterdam, the tree Phylica arborea mixed with ferns.

Although the islands are remote and therefore safe from most human activity and pollution, several introduced species of flora and fauna have damaged the environment.

As part of the French Southern and Antarctic Lands the islands are home to a research base which is working to preserve the original plant and animal life.

Humans have caused other damage to the islands' ecosystems, as much of Amsterdam's woodland was cleared in the 18th and 19th centuries by whalers, sealers, and visitors from passing ships and is struggling to recover.