What You Need to Know About Declining Species


There is no doubt that the number of individuals across species of mammals, birds, reptiles, amphibians, arthropods (insects and arachnids), fish, crustaceans, corals and other cnidarians, and plants have declined, in many cases severely, and that human civilization has had a negative impact on most living things, particularly since the industrial revolution.[1] The devastation of genetically unique populations is an irreversible biodiversity loss. The evidence all points to a global tragedy with a profound loss of biodiversity. [2]

Many of us have seen images depicting large herds of bison running in the US open prairies that no longer exist. Remember enormous flocks of birds congregated in marshes and lagoons that have seen their numbers reduced dramatically, or knew of millions of wild animals participating in The Great Migration of the wildebeest, zebras and Thomson’s gazelles in Africa, along with beautiful and impressive animals such as elephants, giraffes, and rhinos, which -in some cases- are in danger of becoming extinct.

Other people have cherished memories of less imposing animals that nonetheless bring deeply felt emotions, such as the sound of thousands of frogs croaking in the middle of the night, birds visiting a backyard feeder year after year; or millions of bats flying to their resting place at dusk. Others might remember that when traveling by car through the countryside, the windshield ended up covered with hundreds of dead insects, which somehow gave us a sense of abundance, and now hardly ever happens. And bees and bumble bees swarming in considerable numbers very often to our gardens, or in large meadows covered with wildflowers, and now in many places, we hardly see any.

If you lived close to the ocean or spend much time there, you were possibly privy to conversations about abundant fish stocks and a bountiful ocean. And, now you will often hear that fish stocks have declined dramatically or read stories about whales, dolphins and other marine mammals washed up death in beaches[3], occasionally in large numbers.

In the last decades, we have also heard of new species of plants or animals being discovered in tropical forests across the globe, giving us a sense of wonder and possibility; and also that millions of acres of natural forests are being destroyed every year.

Let’s check some facts[4]:

  • The number of wild species living on the land has fallen by 40% since 1970. From forest elephants in central Africa, where poaching rates now exceed birth rates, to the Hoolock gibbon in Bangladesh, and European snakes like the meadow and asp vipers. [5]
  • Marine animal populations have also fallen by 40% overall, with turtles suffering in particular.[6] Hunting, the destruction of nesting grounds and getting drowned in fishing nets have seen turtle numbers fall by 80%.
  • Birds have been heavily affected too.[7] The number of grey partridges in the UK sank by 50%since 1970 due to the intensification of farming, while curlew sandpipers in Australia lost 80% of their number in the 20 years to 2005.
  • Animal populations in freshwater ecosystems plummeted by 75% since 1970. Extinction rates for well-studied North American freshwater animals are estimated to be as high as 4% per decade, five times greater than species losses in terrestrial systems, and rates for less-studied regions and faunas may be as high or higher.[8]
  • Insect populations have declined also. There have long been signs of such a decline. Studies have also shown that populations of European butterflieshave halved since 1990, honeybee colonies have fallen by 59 percent in North American since World War II, and populations of British moths have dropped by 30 percent per decade.[9] In Germany insects have declined by 75% in the last 30 years.[10]
  • About a quarter of coral reefs have already been damaged beyond repair. And 75 percent of the world’s coral reefs are at risk from local and global stresses. Coral reefs are home to more than a quarter of all marine species: crustaceans, reptiles, seaweeds, bacteria, fungi, and over 4000 species of fish make their home in coral reefs.[11]

As reported in the Guardian in 2014[12], “the biggest declines in animal numbers have been seen in low-income, developing nations, while conservation efforts in rich nations have seen small improvements overall. But the big declines in wildlife in rich nations had already occurred long before the new report’s baseline year of 1970 – the last wolf in the UK was shot in 1680. Also, by importing food and other goods produced via habitat destruction in developing nations, rich nations are “outsourcing” wildlife decline to those countries, said Norris. For example, a third of all the products of deforestation such as timber, beef, and soya were exported to the EU between 1990 and 2008.”

Academics and others dedicated to the study of species and the natural world debate if we are already facing a new process of extinction, such as the ones the world has experienced before. Even if that is not the case, we know that besides the species that most people and organizations are focused on because they are in danger to be extinct, all land animals, sea creatures, and plants -for the most part- have seen their numbers severely reduced, with few exceptions.

Many species have disappeared, and many more are following the same path. As reported by The World Conservation Union (IUCN), there are 849 cases of species that have disappeared in the wild since 1500 A.D., and this does not account for thousands of species that disappear before scientists can even describe them[13]. “As of 2006, more than 16,000 species worldwide were threatened with extinction, but this is likely a gross underestimate because fewer than 3 percent of the world’s 1.9 million described species have been assessed by IUCN’s Red List of Threatened Species.”[14]

We also know that some people have argued that species have disappeared before and that this is just part of a natural process. We also know that all other processes of extinctions in the history of the planet happened because of a catastrophic natural event. In some ways what we are experiencing today, says professor Peter Ward from the University of Washington in Seattle, is very much like the dinosaur-killing event of 65 million years ago, when a planet already stressed by rapid changes in climate and sea level was knocked into mass extinction by the impact of asteroids. A very similar scenario has been unfolding in which a single species is having an outsized negative impact over all other species: us the Homo sapiens. In others words, human activity is directly related or has caused the conditions under which most species on Earth have seen their numbers dramatically reduced, almost a thousand of them have already disappeared and approximately 16,000 species worldwide are threatened with extinction.

The marine extinction crisis is not as widely grasped as the crises in tropical forests and other terrestrial biome, says Tundi Agardy[15]. We do not know how many species are in the ocean, and therefore we do not know how many have disappeared or how many are in danger of disappearing. We know that “overfishing is a major global concern. Current assessments cover only 20% of the world’s fish stocks, so the true state of most of the world’s fish populations is still murky. Now, a new method based on catch data and fish characteristics suggests that those unstudied stocks are declining.”[16]

Nearly three-quarters of the world’s commercially fished stocks are overharvested and at risk. Furthermore, the bulk of marine species are undiscovered -we are losing species or unique types within a species- before we even know of them. As a result, the number of known marine extinctions is small due to our lack of knowledge.[17]

What is driving the dramatic reduction of individuals/populations across all species?

  • Overexploitation of species[18] either for human consumption, use, elaboration of byproducts, or for sport.
  • Habitat Loss:
    • Habitat destruction: A bulldozer pushing down trees is the iconic image of habitat destruction. Other ways people directly destroy habitat include filling in wetlands, dredging rivers, mowing fields, and cutting down trees.
    • Habitat fragmentation: Much of the remaining terrestrial wildlife habitat has been cut up into fragments by roads and development. Aquatic species’ habitats have been fragmented by dams and water diversions. These fragments of habitat may not be large or connected enough to support species that need a large territory where they can find mates and food. The loss and fragmentation of habitats makes it difficult for migratory species to find places to rest and feed along their migration routes.
    • Habitat degradation: Pollutioninvasive species, and disruption of ecosystem processes (such as changing the intensity of fires in an ecosystem) are some of the ways habitats can become so degraded, they no longer support native wildlife.[19]
  • Climate Change: As climate change alters temperature and weather patterns, it will also impact plant and animal life. Scientists expect the number and range of species, which define biodiversity, will decline greatly as temperatures continue to rise. The loss of biodiversity could have many negative impacts on the future of ecosystems and humanity worldwide.[20]
  • The spread of non-native species around the world[21]: This is known as “global homogenization of flora and fauna.” Basically, what this means is that you can eat tomatoes in Italy, hunt oryx in Texas, ride horses in Chile, find cane toads in Australia, dig earthworms in eastern North America and catch rats in the Galapagos. None of these things would have been possible without human intervention; and,
  • Other: For example, actions to eliminate a population of animals that is considered a nuisance or a threat to human activities (for example eliminating insects using pesticides).