Wildlife sustains ecosystems and human societies through a web of biological functions that ranges from regulating prey populations and dispersing seeds to pollinating crops and cycling nutrients through soil and ocean. Remove one group of animals and the consequences rarely stay local: forests lose their ability to regrow, crop yields drop, disease transmission shifts, and even carbon storage in the atmosphere changes. The scope of these connections is wider than most people assume, and recent research keeps uncovering pathways that earlier science missed entirely.
How Predators Shape Entire Landscapes
Large predators do far more than kill prey. They set off trophic cascades, chains of ecological effects that ripple down from the top of the food web to the soil itself. In Australian rangelands, research has shown that where dingoes are rare, kangaroo populations surge. That overgrazing strips vegetation, which in turn depletes carbon, nitrogen, and phosphorus in the soil. Where dingoes are common, kangaroo numbers stay in check, plant cover remains intact, and soil nutrients stay healthier. The spatial scale of this effect is enormous, stretching across vast swaths of the continent.1PubMed Central. Removal of an apex predator initiates a trophic cascade that extends from herbivores to vegetation and the soil nutrient pool
These top-down forces matter for conservation policy in ways that are sometimes counterintuitive. Large predators commonly limit populations of both native and introduced prey species as well as smaller predators. That control over mesopredators and herbivores influences biodiversity across entire ecosystems, sometimes even helping to manage the damage caused by invasive species.2Trends in Ecology & Evolution. Trophic cascades help to reconcile conservation with introduced species When predators disappear, the cascade reverses, and the damage compounds over time as unchecked herbivore populations degrade habitats that other species depend on.
The Animals That Build Habitats
Some species reshape the physical environment so dramatically they create entirely new habitats for other organisms. Beavers are the textbook case. By building dams and flooding valleys, they modify hydrology, sediment flow, and water chemistry across whole watersheds, with cascading effects on the plant and animal communities that live there.3PubMed Central. Beaver: Nature’s ecosystem engineers In the Adirondack region of New York, beaver activity increases the number of herbaceous plant species in the riparian zone by over a third compared to areas with no history of beaver occupation, simply by creating habitat variety that would not otherwise exist.4PubMed. An ecosystem engineer, the beaver, increases species richness at the landscape scale
Beavers get most of the attention, but digging mammals perform a less visible version of the same service. In Tasmanian woodlands, the burrows and soil disturbances created by digging marsupials act as traps for organic matter and nurseries for new soil. That freshly turned earth holds more moisture, is softer, and has higher fertility than the undisturbed ground around it, giving seeds a better chance of establishing.5Royal Society Open Science. Ecosystem engineering by digging mammals: effects on soil fertility and condition in Tasmanian temperate woodland These are the kinds of unglamorous ecological roles that rarely make headlines but quietly underpin ecosystem productivity.
Pollination and the Food Supply
About 17 percent of global crop production value depends on pollination services, and those pollinator-dependent crops account for an even larger share of global agricultural trade, roughly 28 percent.6Ecological Economics. Pollinator declines, international trade and global food security: Reassessing the global economic and nutritional impacts That gap between production value and trade share matters: it means the crops most connected to international food markets are disproportionately the ones that need bees, butterflies, and other pollinators.
Modeling what would happen if wild pollinators collapsed across Europe gives a sense of the stakes. Crop yields would fall by roughly 8 percent overall, but the damage would concentrate in nutrient-dense foods. Production of pollination-dependent crops like fruits and vegetables would drop by about 16 percent, driving their prices up by nearly 19 percent. The downstream nutritional hit is real: vitamin A availability across European food supplies would decline by close to 4 percent, with folate taking a similar hit.7Nature. The economic, agricultural, and food security repercussions of a wild pollinator collapse in Europe And it is not just fruits and vegetables at risk. Pollinator-dependent leguminous crops like soybean supply a huge share of global protein, and pollinator-dependent fodder plants like clover and alfalfa feed livestock. A pollinator decline could squeeze both plant-based and animal-based protein supplies simultaneously.8Global Ecology and Conservation. The impact of pollinator decline on global protein production: Implications for livestock and plant-based products
Seed Dispersal, Forest Recovery, and Carbon
The connection between wildlife and climate runs through a channel most people do not think about: seed dispersal. Roughly 81 percent of tropical trees rely on animals to move their seeds, and when those animal populations decline, forest regrowth slows dramatically. Naturally regrowing areas with the least seed-dispersal disruption accumulate aboveground carbon at four times the rate of areas where dispersal has been most severely disrupted. Across lands identified as suitable for reforestation, current levels of animal decline translate into an average 57 percent reduction in local carbon accumulation potential.9PubMed Central. Seed dispersal disruption limits tropical forest regrowth
This is not a hypothetical worry. In Brazil’s Atlantic Forest, simulations show that eliminating the trees dependent on large fruit-eating vertebrates significantly erodes carbon storage, even when only a small proportion of large-seeded tree species are lost.10PubMed Central. Defaunation affects carbon storage in tropical forests And a global meta-analysis of real-world defaunation (as opposed to controlled experiments) found that the extirpation of vertebrates has a clearly negative effect on forest regeneration, with the loss of primates and birds showing the most damaging impacts.11Nature Ecology & Evolution. Quantifying the impacts of defaunation on natural forest regeneration in a global meta-analysis Reforestation policy has historically focused almost entirely on planting trees and preventing logging. This research suggests that protecting the animals who move seeds is just as critical if the goal is to rebuild forests that actually function as carbon sinks.
Free Pest Control on the Farm
Insectivorous bats deliver agricultural value that is easy to overlook until you measure it. In corn fields, experiments using large exclusion structures showed that bats suppress pest larvae enough to reduce crop damage and, as a bonus, limit the fungal growth and toxic compounds that insect pests leave behind. The estimated value of bat-driven pest suppression in corn alone exceeds one billion dollars globally per year.12PubMed Central. Bats initiate vital agroecological interactions in corn In organic apple orchards, excluding bats at night roughly doubled the proportion of yield damaged by codling moth. About 91 percent of trees without bat access had damaged apples, compared to 59 percent where bats could hunt freely.13Journal for Nature Conservation. A bat a day keeps the pest away: Bats provide valuable protection from pests in organic apple orchards
Not every wildlife-based pest control story is a clear success, though. A study comparing hunting perches for raptors against chemical rodenticides in crop fields found that while the perches effectively increased raptor presence and activity, rodent populations still rose at similar rates across all treatment groups, including the one with rodenticides.14PubMed Central. Assessing Birds of Prey as Biological Pest Control: A Comparative Study with Hunting Perches and Rodenticides on Rodent Activity and Crop Health The lesson is not that raptors are useless for rodent control, but that the relationship between predator presence and pest suppression is context-dependent and not always as straightforward as advocates suggest. Bat-based control of flying insects has stronger and more consistent evidence than raptor-based control of rodents.
Nutrients Delivered by Migration
Migrating animals move enormous quantities of nutrients across landscapes. Pacific salmon offer the most thoroughly documented example. Each year, roughly 119 million salmon that escape commercial fisheries return to their spawning grounds, carrying an estimated 14,000 tonnes of nutrients inland, including about 9,000 tonnes of nitrogen and 1,100 tonnes of phosphorus. They also transport thousands of tonnes of omega-3 fatty acids that feed riverine and terrestrial ecosystems after the fish die and decompose.15Nature. Continental-scale nutrient and contaminant delivery by Pacific salmon Higher salmon returns over recent decades have increased nutrient inputs by about 30 percent. There is a less welcome side: the same fish also carry small amounts of mercury, PCBs, and other persistent contaminants from the ocean into freshwater systems. The quantities are tiny compared to the nutrient loads, but they illustrate how wildlife can serve as both a delivery system for ecological benefits and a vector for pollutants that humans introduced in the first place.
Scavengers and Sanitation
Vultures are often treated as incidental background characters, but they perform a sanitation service that has direct consequences for disease risk. By consuming carcasses quickly and efficiently, vultures reduce the time that pathogens have to multiply in decaying tissue and limit transmission to other wildlife, livestock, and people.16PubMed Central. Game Species Management and Ecosystem Health: Leveraging Vulture Scavenging to Improve Carcass Disposal and Health Risk Reduction The collapse of vulture populations in South Asia during the 1990s and 2000s, driven by the veterinary drug diclofenac, provided a grim natural experiment: with vultures gone, feral dog populations surged on the now-unscavenged carcasses, and rabies cases rose. The economic and health costs were substantial, making the case that losing a single functional group of wildlife can create cascading public health problems.
Biodiversity as a Buffer Against Disease
Wildlife diversity also influences how diseases spread to people, through what ecologists call the dilution effect. In many systems, the species most likely to host and transmit pathogens are the ones that persist best when biodiversity drops. Low-diversity communities become dominated by these high-quality reservoir hosts, increasing pathogen transmission. Multiple meta-analyses have found that natural dilution effects are common across diseases of plants, humans, and other animals.17PubMed Central. Dilution effects in disease ecology
For tick-borne pathogens specifically, modeling work has shown that more functionally diverse animal communities result in fewer infectious rodents, which are the primary reservoir for several tick-borne diseases.18PubMed Central. An eco-epidemiological modeling approach to investigate dilution effect in two different tick-borne pathosystems The broader pattern holds for zoonotic disease emergence too: in less-disturbed ecosystems, reservoir hosts are less abundant and non-reservoir species predominate. Biodiversity loss appears to increase human exposure to both new and established zoonotic pathogens.19PubMed Central. Impacts of biodiversity and biodiversity loss on zoonotic diseases This does not mean every forest is a disease shield, but the evidence increasingly suggests that intact ecosystems are less likely to generate the conditions for pathogen spillover into human populations.
Whales and Carbon Sequestration
Great whales influence carbon dynamics in ways that are only now being quantified. They store carbon directly in their massive bodies and export it to the deep ocean when they die and sink. Their nutrient-rich excrement also stimulates phytoplankton growth near the surface, which captures atmospheric carbon dioxide, though this indirect pathway is still poorly understood.20PubMed. Whales in the carbon cycle: can recovery remove carbon dioxide?
Modeling the carbon pump created by five baleen whale species in the southern hemisphere suggests that at pre-whaling abundance, these populations could have sequestered about 400,000 tonnes of carbon per year through carcass sinking alone. Commercial whaling knocked that down to around 60,000 tonnes by the early 1970s. If whale populations recover under current climate projections, sequestration could climb back to roughly 170,000 tonnes per year by 2100, but climate change itself will prevent a full recovery. Without climate impacts, restored whale populations could sequester nearly twice that amount.21PubMed Central. Recovery of carbon benefits by overharvested baleen whale populations is threatened by climate change These numbers are small relative to global emissions, but they highlight how even a single functional group of large animals participates in planetary-scale processes. And carcass sinking is just one piece of the picture; the fertilization of phytoplankton by whale feces may ultimately prove to be the larger carbon contribution.
Wildlife as Pollution Sentinels
Animals accumulate environmental contaminants in their tissues, which makes them useful early-warning systems for pollution that might otherwise go undetected. Black mambas living in urban and industrial areas of southern Africa were found to have significantly higher concentrations of heavy metals in their scales compared to mambas in connected green spaces, revealing fine-scale local pollution patterns that standard environmental monitoring might miss.22PubMed. Black mambas (Dendroaspis polylepis) as novel bioindicators of urban heavy metal pollution This kind of biological monitoring is not new: analysis of a medieval brown bear’s teeth revealed elevated lead, lithium, and zinc concentrations tied to seasonal foraging patterns, representing the earliest known evidence of anthropogenic heavy metal pollution in a wild animal. The finding also demonstrated that human industrial threats to wildlife extend back far further in history than most people assume.23PubMed. Earliest evidence for heavy metal pollution on wildlife in Middle Age Europe
Medicine Hidden in Venom
Some of the most medically important compounds in modern pharmacology were derived from wildlife that most people would rather avoid. Peptide toxins isolated from snake venoms target ion channels, membrane receptors, and blood-clotting components with remarkable precision. Several FDA-approved drugs originated in snake venom research, including Captopril (used for high blood pressure), Eptifibatide, and Tirofiban (both used to prevent blood clots). Beyond these approved medications, numerous other venom-derived compounds are in preclinical or clinical trials for a range of therapeutic applications.24PubMed Central. Snake Venoms in Drug Discovery: Valuable Therapeutic Tools for Life Saving The broader point is that wild species represent a vast library of bioactive molecules refined by millions of years of evolution. Every extinction closes a door that pharmaceutical science might have walked through.
Wild Genes for Future Crops
Wild relatives of domesticated crops carry genetic diversity that modern cultivars have lost through centuries of selective breeding for yield under favorable conditions. Those wild relatives have evolved tolerances to drought, heat, salinity, and disease that crop breeders are now racing to incorporate into commercial varieties as climate change intensifies.25PubMed Central. Crop Wild Relatives: A Valuable Source of Tolerance to Various Abiotic Stresses For Brassica crops like broccoli, cabbage, and canola, wild relatives show increased tolerance to both pests and environmental stress because they were never subjected to the narrow selection pressures that optimized domesticated lines for maximum yield under ideal conditions.26PubMed Central. Using wild relatives and related species to build climate resilience in Brassica crops Researchers have described this strategy as “introgressiomics,” a systematic effort to identify and transfer useful traits from wild relatives into elite crop varieties before climate shifts make current cultivars unviable.27Euphytica. Introgressiomics: a new approach for using crop wild relatives in breeding for adaptation to climate change The survival of these wild plant populations depends on the broader ecosystems and animal communities that pollinate, disperse, and protect them, which links crop breeding directly back to wildlife conservation.
Ecotourism and Mental Health
Wildlife-based ecotourism channels money into communities that might otherwise see little economic reason to preserve habitat. Entrance fees, conservation levies, voluntary donations, and the indirect revenue from travel and lodging taxes can make living ecosystems more financially valuable than the short-term gains from converting them to farmland or extractive use.28International Journal of Geoheritage and Parks. Ecotourism, biodiversity conservation and livelihoods: Understanding the convergence and divergence The economic argument does not work everywhere and has its own distortions, but where ecotourism is well managed, it creates a feedback loop in which conservation generates revenue that funds further conservation.
The psychological benefits of wildlife encounters are harder to monetize but increasingly documented. Research on human-animal interactions in natural settings has found that people report feelings of love, belonging, fulfillment, and perspective during and after encounters with wild animals, with links to broader mental wellbeing and nature connectedness.29PubMed Central. Human-Animal Interactions: Expressions of Wellbeing through a “Nature Language” Even everyday encounters count. Interview-based studies have found that people describe watching neighborhood wildlife, even something as simple as hummingbirds at a feeder, as a source of peace and calm that they rely on for emotional balance.30SSM – Qualitative Research in Health. Evaluating how varied human-wildlife interactions affect physical, mental, social, and spiritual health
Indigenous Knowledge and Wildlife Stewardship
For Indigenous communities across North America and elsewhere, wildlife is not an external resource to be managed but a relative embedded in cultural identity and daily life. Traditional Ecological Knowledge, described as the accumulated relationship between Indigenous peoples and their ecosystems, is increasingly recognized in academic and professional wildlife management despite the field’s historical dominance by Western scientific frameworks.31The Journal of Wildlife Management. State of Traditional Ecological Knowledge in the wildlife management profession In Wisconsin, Indigenous peoples manage forests for mature conditions, accommodate wolves and other predators, and hunt deer in ways designed to sustain traditional livelihood values rather than maximize harvest.32Ecology and Society. First Stewards: Ecological Outcomes of Forest and Wildlife Stewardship by Indigenous peoples of Wisconsin, USA
Several tribal wildlife stewardship programs in California illustrate how Indigenous worldviews can produce conservation outcomes that benefit both ecosystems and communities. The Maidu Summit Consortium’s beaver restoration project, the Karuk Tribe’s elk management program, and the Yurok Tribe’s condor recovery effort each connect ecological restoration with cultural revitalization and environmental justice in ways that conventional management models rarely achieve.33Environmental Science & Policy. Back to the future: Indigenous relationality, kincentricity and the North American Model of wildlife management The practical takeaway is that communities with deep cultural ties to wildlife often manage ecosystems in ways that sustain biodiversity, and those approaches deserve a larger seat at the policy table.
Why Redundancy in Nature Is Not Waste
People sometimes ask why it matters if a few species disappear when others seem to fill similar roles. The answer lies in what ecologists call functional redundancy: when multiple species perform overlapping jobs, the ecosystem can absorb the loss of one without collapsing. A meta-analysis found that the correlation between functional redundancy and ecological stability or resilience is generally positive, meaning communities with more redundant species tend to weather disturbances better.34Ecosphere. Does functional redundancy affect ecological stability and resilience? A review and meta‐analysis Think of it as insurance: the “extra” species are not doing nothing, they are providing a buffer against an uncertain future. When redundancy erodes, ecosystems become more brittle. A single disease outbreak, extreme weather event, or habitat disruption can then eliminate a function entirely, with cascading effects of the kind described throughout the examples above. The challenge is that you rarely know which species were redundant until they are gone and the system starts to fail.