Why would it be hard for a cactus to live on a channel island?

Cacti typically thrive in arid environments with well-draining soil and plenty of sunlight, conditions that may not be consistent on a channel island. These islands often have varying climates, including higher humidity and less predictable rainfall, which can be detrimental to a cactus's survival. Additionally, limited soil nutrients and competition with other plant species can further challenge a cactus's ability to establish and thrive in such ecosystems.