The animal kingdom encompasses millions of species, from microscopic zooplankton to the largest whales. This vast biological variety, known as fauna, interacts with the planet in ways far more extensive than just providing food or companionship. The importance of animals extends deep into the processes that sustain the environment, drive global commerce, and underpin human advancement. Their presence shapes the physical world and dictates the health and function of the complex systems that make life on Earth possible.
Maintaining Earth’s Ecosystems
Animals perform irreplaceable functions that maintain the physical and biological integrity of almost every habitat on Earth. Certain species are known as “keystone species” because their influence is disproportionately large compared to their actual numbers. For instance, the reintroduction of wolves to Yellowstone National Park regulated elk and deer populations. This allowed previously over-browsed vegetation to recover, which stabilized riverbanks and provided habitat for birds and beavers.
Beavers, often called ecosystem engineers, physically modify their surroundings by building dams that create wetlands. These aquatic habitats slow water flow, filter pollutants, and provide shelter for diverse plant and animal species. In marine environments, sea otters act as keystone predators by consuming sea urchins. This prevents the urchins from destroying kelp forests that serve as nurseries for fish and invertebrates.
Many animals are the primary drivers of nutrient cycling and soil health, processes fundamental to plant growth worldwide. Scavengers and decomposers, from vultures to earthworms and insects, remove waste and break down organic matter, returning nitrogen and other elements to the soil. Prairie dogs aerate the soil with their burrowing activity and spread nutrients, enriching the ground and supporting other species that use their abandoned homes for shelter.
Mutualistic relationships, where both parties benefit, are also maintained by animal activity. Pollinators, primarily insects like bees and butterflies, are responsible for the reproduction of nearly 90% of the world’s flowering plant species. Large mammals and birds also play a significant role in seed dispersal by consuming fruits. They deposit the seeds far from the parent plant, facilitating forest regeneration and maintaining high plant diversity.
Essential Resources and Global Economy
The economic contribution of animals is measured in hundreds of billions of dollars, touching sectors from food production to global tourism. Livestock and fisheries are foundational to global food security, providing protein and nutrients for billions of people worldwide. This production system supports a massive workforce, with an estimated 58.5 million people globally engaged in fisheries and aquaculture alone in 2020.
Animals also supply valuable raw materials that drive significant industries. The global market for animal textiles includes wool, silk, and specialty fibers like alpaca and cashmere. Wool accounts for a substantial portion of natural fiber production, and the silk market is projected to reach $31.7 billion by 2030.
Employment related to animal production and care is extensive and diverse, encompassing traditional farming, ranching, and fishing, as well as specialized roles. In the United States, the largest animal-related occupation is farming and agricultural management, employing hundreds of thousands of people. This commercial ecosystem also includes:
- Veterinarians and veterinary technicians
- Feed suppliers
- Food processors and distributors
Wildlife-based ecotourism represents another multi-billion-dollar economic sector. The viewing of animals through safaris, whale watching, and bird watching drives local and national economies. This financial incentive creates a powerful local motivation for conserving natural habitats. The continued presence of healthy animal populations directly translates into sustainable revenue.
Advancing Human Health and Scientific Understanding
Animals serve as biological models for understanding fundamental life processes and developing treatments for human diseases. Studying the unique biology of different species offers insights into health and immunity. For instance, researchers study bats for their ability to carry numerous viruses without becoming ill, which informs research into human immune response.
The development and testing of modern vaccines and pharmaceuticals rely on animal models to establish safety and efficacy before human trials begin. This was evident during the development of COVID-19 vaccines, where initial testing involved ferrets, non-human primates, and mice. Research on animals has also been crucial in developing treatments for chronic conditions, including therapies for diabetes, cancer, and heart disease.
Breakthroughs are sometimes derived from unique animal properties, such as the discovery that nanobodies, generated by llamas and camels, can effectively target viruses. The HPV vaccine, which prevents cervical cancer, was inspired by research on a vaccine protecting cattle from the bovine papilloma virus. These models advance human medicine and contribute to a deeper understanding of genetics, embryonic development, and the nervous system.
Psychological and Social Well-being
The connection between humans and animals offers substantial benefits that enhance mental and social health. Companion animals provide consistent social support, which is valuable for individuals experiencing loneliness or anxiety. This bond fulfills a deep human need for attachment, contributing significantly to emotional stability.
Interacting with animals triggers measurable physiological responses that promote relaxation and reduce stress. Petting a dog or cat can lower the stress hormone cortisol while increasing oxytocin, a hormone associated with bonding. This interaction also leads to reduced blood pressure and heart rate, mitigating the effects of chronic stress.
Animals also play structured roles in human care through specialized training as service and therapy providers. Service animals offer physical assistance to people with disabilities. Therapy animals are used in settings like hospitals and nursing homes to improve emotional and psychological states. These interventions help manage conditions such as depression and post-traumatic stress disorder.
For children, growing up with animals fosters emotional development by teaching responsibility and empathy. Pets offer unconditional love and a non-judgmental presence, providing a secure outlet for emotional expression. The routines associated with pet care, such as feeding and grooming, provide structure to the lives of their owners.