nature & planetanalysisThe Conversation
Life after death: From burned trees to bleached corals, how dead organisms live on as the building blocks of new life
Dead organisms keep shaping ecosystems long after they die, a principle ecologists call ecological memory. Fallen trees, dead coral skeletons, oyster shells and leaf litter can either help or block recovery after a disaster. Across 10 ecosystems studied in a long-term US research network, dead foundation species significantly increased or decreased living ones in nine, with the kelp forest the only exception. In roughly half of those cases they hindered recovery; a layer of fallen branches in Puerto Rico's rainforest blocks sunlight for seedlings, while dead mangrove roots gain nutrients from storm debris and regrow faster. Dead coral skeletons can instead be overgrown by seaweed that prevents corals returning, so the outcome depends on the ecosystem.
Foundation species such as trees and corals build structures that other life relies on. When they die, their remains keep their physical structure for years. That structure can shelter new seedlings and recycle nutrients, or it can block light, trap sediment or let algae spread, depending on what the remains look like and what the disturbance was.
Managers can use this knowledge after storms and heat waves, for example by felling dead trees into nurse logs or laying oyster shells on mud flats to rebuild habitat. As extreme events grow more frequent, what dies in a disaster will increasingly determine how fast nature recovers.
A fallen log that seedlings grow on is called a nurse log, because the decaying wood gives young trees soft, nutrient-rich ground.
