Green plants are the foundation that nearly all animal life depends on. They produce the oxygen animals breathe, form the base of almost every food chain on Earth, provide physical shelter, regulate climate, and cycle water back into the atmosphere. Remove green plants, and animal life as we know it collapses within weeks.
Plants Produce the Oxygen Animals Breathe
Every breath an animal takes relies on oxygen generated through photosynthesis. Green plants on land, along with algae and photosynthetic bacteria in the ocean, are responsible for virtually all of Earth’s atmospheric oxygen. NOAA estimates that roughly half of global oxygen production comes from the ocean, primarily from plankton and tiny photosynthetic bacteria. The other half comes from terrestrial plants: forests, grasslands, and crops. A single species of ocean bacteria, Prochlorococcus, produces up to 20% of the oxygen in the entire biosphere, more than all tropical rainforests combined.
Land plants still matter enormously, though. Forests and other vegetation maintain steady oxygen levels across continents and create the breathable microclimates animals inhabit day to day. Without ongoing photosynthesis replenishing atmospheric oxygen, concentrations would eventually decline to levels that couldn’t support animal respiration.
The Base of Nearly Every Food Chain
Green plants capture sunlight and convert it into chemical energy stored in leaves, fruits, seeds, and roots. This makes them “producers,” the only organisms in most ecosystems that create new energy from scratch. Every herbivore, from a caterpillar to an elephant, feeds directly on that stored energy. Carnivores then get their energy by eating herbivores, and so on up the chain.
Energy transfer between levels is inefficient. On average, only about 10% of the energy stored in one level of a food chain passes to the next. This “10 percent rule” means that a fox eating a rabbit receives just 10% of the energy the rabbit got from the plants it ate, and the rabbit itself captured only 10% of the plant’s stored energy. This steep drop-off is the reason ecosystems support far more herbivores than top predators, and why plants must be enormously abundant to keep any food web running.
Essential Vitamins Animals Can’t Make
Plants aren’t just calories. They supply vitamins and minerals that many animals cannot synthesize on their own. Plant-based foods are the primary natural source of vitamin C (with about 76% bioavailability when consumed), the precursor to vitamin A found in orange and leafy green vegetables (beta-carotene), thiamin, riboflavin, and vitamin K. Most animals that eat plants, or eat other animals that ate plants, ultimately trace these nutrients back to vegetation.
Vitamin C is a good example. Most mammals lost the ability to produce it internally millions of years ago. Primates, guinea pigs, and fruit bats all depend on plant foods to avoid deficiency. Herbivores like deer and rabbits get their full vitamin profile from foliage, while carnivores obtain some of these same nutrients secondhand by consuming the organs and gut contents of their plant-eating prey.
Shelter, Nesting, and Habitat Structure
Plants do more than feed animals. They physically house them. Forests, grasslands, shrublands, and wetlands all create the three-dimensional structures animals need for nesting, hiding from predators, raising young, and hunting. Research on forested landscapes shows that vertical complexity, meaning variation in canopy height and layering, is positively associated with greater diversity of birds, beetles, and bats. When a forest has tall canopy trees, a mid-level understory, and ground-level shrubs, it creates distinct microhabitats that allow many species to coexist in the same area.
This relationship is sometimes called the “height variation hypothesis”: the more varied the canopy structure, the more niches available for different species to occupy. A woodpecker drills into tall trunks, a warbler nests in mid-level branches, and a ground-nesting bird shelters under low shrubs, all in the same forest. Simplify that plant structure by clearing vegetation or converting forest to monoculture, and animal diversity drops sharply.
Regulating Water and Weather
Plants are powerful water pumps. They pull moisture from the soil through their roots and release it into the atmosphere through tiny pores on their leaves, a process called transpiration. This moisture forms clouds and eventually falls as rain. In the Amazon basin, tree transpiration accounts for roughly 22% of total precipitation. In other words, the forest generates a significant share of its own rainfall.
This matters to animals because consistent rainfall sustains the rivers, wetlands, ponds, and moist soils that countless species depend on for drinking water, breeding habitat, and food. When large areas of forest are cleared, local rainfall patterns can shift, streams can dry up, and the animals that relied on that water lose their habitat. Tropical amphibians, freshwater fish, and the insects that form the base of aquatic food webs are especially vulnerable to these changes.
Carbon Storage and Climate Stability
Forests and other plant-rich ecosystems absorb carbon dioxide from the atmosphere and store it in wood, roots, and soil. This carbon storage helps regulate the planet’s temperature. Without it, more carbon dioxide accumulates in the atmosphere, intensifying the greenhouse effect, raising global temperatures, and disrupting the climate patterns animals have adapted to over thousands of generations.
The connection between plant health and animal survival runs both directions. When forests burn at high severity or are cleared, they release large pulses of stored carbon. That accelerates warming, which in turn increases drought, pest outbreaks, and wildfire risk, creating a feedback loop that degrades habitat further. Restoring low-severity prescribed fire and protecting peatlands by reconnecting waterways are strategies that keep carbon in the ground while maintaining the habitat conditions wildlife needs. Peatland rewetting, for instance, reduces smoldering underground burns while supporting groundwater recharge that benefits local ecosystems.
Animals That Can’t Survive Without One Plant
Some animal-plant relationships are so tight that the animal literally cannot survive or reproduce without a specific plant species. Yucca moths and yucca plants are a striking example. The moths have specialized mouthparts found in no other insect group, shaped specifically to collect and deposit yucca pollen. Without yucca plants, yucca moths have no food source for their larvae and no way to reproduce. The plant, in turn, almost never gets pollinated by any other species.
Fig wasps and fig trees share a similarly locked-in relationship that has persisted for millions of years. Each fig species typically relies on a single wasp species for pollination, and the wasp depends entirely on that fig for its life cycle. These obligate mutualisms highlight how deeply intertwined animal and plant survival can be. Lose the plant, and the animal vanishes with it.
Animals That Use Plants as Medicine
Beyond food and shelter, some animals actively seek out specific plants to treat illness or parasites, a behavior scientists call zoopharmacognosy. Baboons in Ethiopia eat the leaves of a particular plant to fight the flatworms that cause schistosomiasis. Pregnant lemurs in Madagascar chew tamarind and fig leaves and bark to kill parasites, stimulate milk production, and improve their chances of a successful birth.
Bonobos in Central Africa have been observed carefully placing leaves of a specific shrub flat on their tongues, a behavior researchers interpret as a kind of time-release medicinal capsule. The leaves appear to have both a scouring and antiparasitic effect as they pass through the digestive system. These behaviors suggest that the importance of plants to animals extends well beyond basic nutrition into something closer to a pharmacy that animals have learned to use over evolutionary time.