The planet is undergoing a sixth mass extinctionthe sixth time in the history of life on Earth that global fauna has experienced a major collapse in numbers.Historically, mass extinctions have been caused by catastrophic events like asteroid collisions. This time, however, human activities are to blame. The primary culprits are deforestation, mining, and carbon-dioxide emissions that cause the planet to heat up.As a result, insects are dying off at record rates, animal species are experiencing "biological annihilation," and invasive aliens are driving native species to extinction.The phrase "mass extinction" typically conjures up images of the asteroid crash that led to the twilight of the dinosaurs.Upon impact, that 6-mile-wide space rock caused a tsunami in the Atlantic Ocean, along with earthquakes and landslides up and down what is now the Americas. A heat pulse baked the Earth, and the Tyrannosaurus rex and its compatriots died out, along with 75% of the planet's species.Although it may not be obvious, another devastating mass extinction event is taking place todaythe sixth of its kind in Earth's history. The trend is hitting global fauna on multiple fronts, as hotter oceans, deforestation, and a climate changedrive animal populations to extinction in unprecedented numbers.Read More:Insects are dying off at record ratesan ominous sign we're in the middle of a 6th mass extinctionA 2017 study found that animal species around the world are experiencing a "biological annihilation," and that our current mass extinction episode has proceeded further than most assume."Here are 12 signs that the planet is in the midst of the sixth mass extinction, and why human activity is primarily to blame.SEE ALSO:Scientists say we're witnessing the planet's sixth mass extinction ' and 'biological annihilation' is the latest signInsects are dying off at record rates. Roughly 40% of the world's insect species are in decline.A 2019 study found that the total mass of all insects on the planets is decreasing by 2.5% per year.If that trend continues unabated, the Earth may not have any insects at all by the year 2119."In 10 years you will have a quarter less, in 50 years only half left, and in 100 years you will have none," Francisco Sanchez-Bayo, a co-author of that study, told The Guardian.That's a major problem, since insects like bees, butterflies, and other pollinators perform a crucial role in fruit, vegetable, and nut production. Plus, bugs are food sources for many bird, fish, and mammal species (some of which humans rely on for food).Earth appears to be undergoing a process of "biological annihilation." As many as half of the total number of animal individuals that once shared the Earth with us are already gone.A 2017 study looked at all animal populations planet-wide (not just insects) by examining 27,600 vertebrate speciesabout half of the overall total that we know exist. They found that more than 30% of them are in decline.Some species are facing total collapse, while certain local populations of others are going extinct in specific areas. That's still cause for alarm, since the study authors said these localized population extinctions are a "prelude to species extinctions."So even declines in animal populations that aren't yet categorized as endangered is a worrisome sign.More than 26,500 of the world's species are threatened with extinction, and that number is expected to keep going up.According to the International Union for the Conservation of Nature (IUCN) red list, more than 27% of all assessed species on the planet are threatened with extinction. Currently, 40% of the planet's amphibians, 25% of its mammals, and 33% of its coral reefs are threatened.The IUCN predicts that 99.9% of critically endangered species and 67% of endangered species will be lost within the next 100 years.See the rest of the story at Business Insider Click here to read full news..