The spread of species beyond their native habitat is a human-made environmental change on a global scale. Among vascular plants, over 16,000 species have now permanently settled in foreign countries.

Erik Irmer has been documenting the spread of invasive plant and animal species that disrupt native ecology across Europe. He focuses on humans’ interactions with these plants and animals. Aliens is p ...

Photosynthesis changed Earth in powerful ways. When photosynthetic organisms appeared, it led to the Great Oxygenation Event. That allowed multicellular life to evolve and resulted in the ozone layer.