A producer is any organism that makes its own food from sunlight or chemical energy, forming the base of every food web on Earth. Plants, algae, and certain bacteria are all producers. Every animal in a food web depends on producers either directly (by eating them) or indirectly (by eating something that ate them), which is why producers occupy the first trophic level in any ecosystem.
How Producers Make Their Own Food
Most producers use photosynthesis. They absorb sunlight and combine water from the soil with carbon dioxide from the air to create glucose, a simple sugar that stores energy. Oxygen is released as a byproduct. This is the process that powers nearly every forest, grassland, ocean surface, and freshwater lake on the planet. Plants, algae, and a type of bacteria called cyanobacteria all photosynthesize.
A smaller group of producers use a different process called chemosynthesis. Instead of sunlight, these organisms pull energy from chemical reactions involving compounds like hydrogen sulfide or methane. Chemosynthetic bacteria thrive in places where sunlight never reaches: hydrothermal vents on the ocean floor, cold seeps where methane bubbles up through sediment, and deep underground rock formations. These bacteria form the foundation of entire ecosystems in total darkness, supporting worms, clams, mussels, and other animals that cluster around vent sites.
Why Producers Are the First Trophic Level
Scientists organize food webs into trophic levels based on how organisms get their energy. Producers sit at the bottom, the first trophic level, because they don’t consume other organisms. Herbivores that eat producers make up the second level. Carnivores that eat herbivores form the third, and so on up the chain.
This structure means energy flows in one direction: from producers upward. Only a fraction of the energy at each level passes to the next, which is why ecosystems always need far more producers than top predators. Of all the solar energy hitting the outer edge of Earth’s atmosphere, producers on land capture roughly 0.06% of it as usable biological energy. That tiny percentage fuels virtually all terrestrial life.
Producers on Land vs. in Water
On land, the familiar producers are vascular plants: trees, grasses, shrubs, and crops. Mosses and lichens also contribute, especially in tundra and alpine environments where larger plants struggle. Tropical evergreen forests are the most productive land ecosystems, generating roughly twice the biological energy per square meter as boreal forests and nearly ten times that of deserts.
In oceans and freshwater, the dominant producers are phytoplankton, microscopic photosynthetic organisms that drift near the surface. Algae, seagrasses, and photosynthetic bacteria also contribute. In the open ocean, phytoplankton are consumed by zooplankton and small crustaceans like krill, which are then eaten by fish, which feed larger predators. It’s the same producer-to-consumer pattern as on land, just with organisms you can barely see doing the heavy lifting at the bottom.
One striking difference between land and ocean food webs is the ratio of producer biomass to consumer biomass. On land, the total mass of plants dwarfs the total mass of animals. In the ocean, the pattern flips: roughly 1 billion metric tons of producer biomass supports about 5 billion metric tons of consumer biomass. This “inverted pyramid” works because phytoplankton reproduce so rapidly that a small standing population can continuously feed a much larger population of consumers.
What Happens When Producers Disappear
Because every food web is built on producers, losing them triggers a collapse that ripples upward through every trophic level. An increase in the number of producers generally leads to more herbivores, which supports more predators. The reverse is equally true: a decline in producers can devastate an entire food chain. Easter Island offers a well-studied example. Overharvesting of the island’s tree population set off a cascade of feedback loops that destabilized agriculture, allowed rat populations to explode, and ultimately contributed to a crash in the human population.
Climate change is creating a modern version of this problem in the oceans. Rising sea surface temperatures and shifts in water mixing patterns are altering the conditions phytoplankton need to thrive. Research published in Nature found that global ocean productivity is likely declining faster than climate models currently predict, because those models underestimate how sensitive phytoplankton growth is to warming waters. Even under optimistic climate scenarios that currently project stable ocean productivity, the real declines may be significant, with consequences for the marine food web, fisheries, and the ocean’s ability to absorb carbon dioxide.
Producers vs. Consumers vs. Decomposers
A food web has three broad categories of organisms. Producers make energy from nonliving sources. Consumers, including herbivores, carnivores, and omnivores, get their energy by eating other organisms. Decomposers, like fungi and certain bacteria, break down dead material and recycle nutrients back into the soil or water, where producers can use them again.
Producers are the only group that converts nonliving energy into the biological fuel everything else runs on. Without them, consumers would have nothing to eat and decomposers would have nothing to break down. That’s why every food web diagram starts with a producer at the base, whether it’s a towering oak tree in a temperate forest or a single-celled phytoplankton drifting in the Pacific.