Credit:
Baz Ratner/Reuters
The world's largest land animals are capable of complex feelings and thoughts, and have great memory storage and recall in their five-kilogram brains. They attract eco-tourism, which protects wilderness for many species, and are an important link in ecosystems, creating watering holes and spreading seeds for new growth. Elephants are under threat from poaching — over 20,000 are killed for their tusks and skin every year — as well as habitat loss from expanding human populations and climate change.
Insects
Credit:
Mike Blake/Reuters
Insects collectively make up 80 percent of all the world's known species — with 200 million insects for every human on Earth. But overall populations have declined 45 percent over the past four decades, causing risks to plant pollination necessary for food production.
Insects are a key component of global ecosystems: Some insects keep other bugs from destroying crops, while others are a food source for other species. Insects are the most vulnerable to climate change, and are also endangered by habitat loss, pesticide use and invasive species.
Trees
Credit:
Alexander Kuznetsov/Reuters
Forests play a vital role in ecosystems: Regulating and maintaining carbon balance; providing shelter for animals; creating nutrient-rich soil; and contributing to the water cycle. Trees are also a major economic contributor through the forestry industry. They are under threat from deforestation, climate change, invasive insects and fires.
Plants
Credit:
Darrin Zammit Lupi/Reuters
There are more than 380,000 different plant species on Earth, that provide us with food, herbal and pharmaceutical medicine and oxygen. Climate change degrades the soil they grow in and raises sea levels.
Invasive species create competition for resources to the detriment of native plants, while habitat loss comes in the form of urban or agricultural development and fires. Pesticides and insecticides can harm plants and their pollinators, while crop patents reduce biodiversity.
Birds
Credit:
Amir Cohen/Reuters
There are roughly 11,000 species of birds, with nearly 40 percent facing significant decline. Birds are scavengers, eliminating waste and remains and eating unwanted agricultural pests. Migratory birds help move seeds and nutrients during their travels. Bird-watching contribute some $40 billion in revenue annually in the United States alone. Among the threats to these creatures are habitat loss, deforestation, climate change and severe weather, plastic and pesticide pollution, and illegal trafficking.
Sharks
Credit:
Hugh Gentry/Reuters
Humans are the greatest threat to these apex predators, which have no known marine predators. Sharks maintain the balance of marine populations below them in the food chain. Without sharks, mid-level species would overconsume creatures at the bottom of the food chain.
It can also affect human food supply: When sharks disappear, fish stocks that humans rely on for industry also collapse. Between 2000 and 2010, some 100 million sharks were killed annually — many hunted for their meat and fins or caught by trawling boats as bycatch. Climate change alters their habitats, affecting their ability to reproduce and find food.
Fish
Credit:
Toru Hanai/Reuters
There are an estimated 32,000 different species of fish worldwide, 33 percent of which are being fished at unsustainable levels. Overfishing is a destabilizing force in marine ecosystems that affects the entire aquatic food web.
Fish are also an economic driver, with some 120 million people dependent on these species for their incomes. Climate change disrupts their migration, reduces their sizes and threatens the reefs and other habitats that they shelter in. Pollution is also a major threat, with chemicals, waste, fertilizer and oil spills causing harm to fish populations and affecting the seafood that humans eat.
Crustaceans
Credit:
Alexandre Meneghini/Reuters
These creatures with exoskeletons are some of the oldest animals on Earth. More than 50,000 known species can be found in fresh and saltwater habitats, playing an important role as food sources for marine animals, recycling nutrients as filter feeders, and decomposing dead organisms.
Crustaceans are also economically important: Blue crabs in the Chesapeake Bay of the US generated an estimated $78 million in 2009 alone. They are threatened by ocean acidification which weakens their shells, loss of habitat on coral reefs, overfishing, and plastic pollution — ingesting microplastics that can travel up through the food chain.
Sea turtles
Credit:
David Gray/Reuters
These marine reptiles are some of the oldest creatures on Earth, and can be found around the world in tropical and subtropical areas. Though they lay their eggs in sandy coastal areas, they spend their entire lives at sea, feeding on seagrass and foraging in coral reefs.
Demand for their eggs, meat, skin and shells has led to a rapid decline in their populations. Sea turtles are also threatened by coastal development and human disruption of nesting sites, becoming bycatch in fishing nets and lines, mistaking plastic pollution for food, and global warming.
Great apes
Credit:
Darren Whiteside/Reuters
Earth Day: Species at risk