Among the most critical steps is the 30x30 campaign, which will protect wildlife places and wildlife habitat, including oceans, rivers, forests, deserts and swamps.
Unlike past mass extinctions, caused by events like asteroid strikes, volcanic eruptions, and natural climate shifts, the current crisis is almost entirely caused by us — humans. In fact, 99 percent of currently threatened species are at risk from human activities, primarily those driving habitat loss, introduction of exotic species, and global warming [ 3 ].
Because the rate of change in our biosphere is increasing, and because every species' extinction potentially leads to the extinction of others bound to that species in a complex ecological web, numbers of extinctions are likely to snowball in the coming decades as ecosystems unravel.
Species diversity ensures ecosystem resilience, giving ecological communities the scope they need to withstand stress. Thus while conservationists often justifiably focus their efforts on species-rich ecosystems like rainforests and coral reefs — which have a lot to lose — a comprehensive strategy for saving biodiversity must also include habitat types with fewer species, like grasslands, tundra, and polar seas — for which any loss could be irreversibly devastating.
And while much concern over extinction focuses on globally lost species, most of biodiversity's benefits take place at a local level, and conserving local populations is the only way to ensure genetic diversity critical for a species' long-term survival.
In the past years, we know of approximately 1, species that have gone extinct, from the woodland bison of West Virginia and Arizona's Merriam's elk to the Rocky Mountain grasshopper, passenger pigeon and Puerto Rico's Culebra parrot — but this doesn't account for thousands of species that disappeared before scientists had a chance to describe them [ 4 ].
Nobody really knows how many species are in danger of becoming extinct. Noted conservation scientist David Wilcove estimates that there are 14, to 35, endangered species in the United States, which is 7 to 18 percent of U. The IUCN has assessed roughly 3 percent of described species and identified 16, species worldwide as being threatened with extinction, or roughly 38 percent of those assessed.
In its latest four-year endangered species assessment, the IUCN reports that the world won't meet a goal of reversing the extinction trend toward species depletion by [ 5 ]. What's clear is that many thousands of species are at risk of disappearing forever in the coming decades. Scientists estimate that a third or more of all the roughly 6, known species of amphibians are at risk of extinction [ 6 ]. Frogs, toads, and salamanders are disappearing because of habitat loss, water and air pollution, climate change, ultraviolet light exposure, introduced exotic species, and disease.
Because of their sensitivity to environmental changes, vanishing amphibians should be viewed as the canary in the global coal mine, signaling subtle yet radical ecosystem changes that could ultimately claim many other species, including humans. BIRDS Birds occur in nearly every habitat on the planet and are often the most visible and familiar wildlife to people across the globe.
As such, they provide an important bellwether for tracking changes to the biosphere. Declining bird populations across most to all habitats confirm that profound changes are occurring on our planet in response to human activities. A report on the state of birds in the United States found that 31 percent of the species in the country are of conservation concern [ 7 ].
Habitat loss and degradation have caused most of the bird declines, but the impacts of invasive species and capture by collectors play a big role, too. FISH Increasing demand for water, the damming of rivers throughout the world, the dumping and accumulation of various pollutants, and invasive species make aquatic ecosystems some of the most threatened on the planet; thus, it's not surprising that there are many fish species that are endangered in both freshwater and marine habitats.
The American Fisheries Society identified species of freshwater or anadromous fish in North America as being imperiled, amounting to 39 percent of all such fish on the continent [ 8 ]. Marilyn Renfree, a marsupial specialist at the University of Melbourne, says that biologically speaking, "marsupials are every bit as good as other mammals—and in some ways superior.
Mike Archer, director of the Australian Museum, also believes that the pouch has its advantages. After having two eggs fertilized, a kangaroo mother may have only one egg fully develop. Should food or water become scarce and the firstborn infant die, the embryo-in-reserve can implant itself after conditions improve.
In an arid land such as Australia, these conditional pregnancies can be the best strategy. But marsupials remain much less common than other mammals. Opossums and other marsupials exist in North and South America, but Australia is the only continent where marsupials—and monotremes—still rule. Kangaroos, koalas, platypuses, and wombats: Why does Australia retain these supposedly antiquated mammals? According to the Sherwin-Williams model, marsupials, advanced mammals themselves million years ago, migrated into Gondwana ahead of placentals.
They simply got on board the Antarctic-Australian landmass before it broke away from the rest of Gondwana. Placentals arrived too late—the Australian ship had already sailed. That theory made a lot of sense until the late s, when some revealing fossils began turning up in various parts of the old Gondwana—Patagonia, Madagascar, and Australia.
The new evidence, once again, came in the form of jawbones and teeth—a particular type known as tribosphenic molars. Such teeth work like a mortar and pestle, a further improvement on the slicing teeth of earlier mammals. The ancestor of marsupials and placentals had tribosphenic teeth. Thus the discovery in the Southern Hemisphere of tribosphenic teeth as old as million years, or 25 million years older than any found in the north, complicates the north-south model.
Some explain the presence of these southern tribosphenic teeth by saying they must have developed independently in both hemispheres. Others say the innovation was too intricate to have evolved twice and that mammals must have evolved in the south, with subsequent generations moving north. The tribosphenic controversy gets even deeper in Australia, where the husband-and-wife team of Tom Rich of the Museum of Victoria and Pat Vickers-Rich of Monash University have turned up three different mammals with tribosphenic teeth dating back million years.
The Riches say that these mammals weren't simply on the way to becoming placental, they were placental—something like hedgehogs, in fact. Opponents of the Riches' theory argue that placentals—and certainly not the relatively advanced hedgehogs—were not supposed to be anywhere near Australia so long ago.
Eomaia, that early forerunner of placentals, lived in Asia. If the Riches are right, we have to rethink how placentals traveled from Asia to the Southern Hemisphere. Rather than traveling down the Americas, Eomaia may have found an island-hopping shortcut to Australia.
Or perhaps placentals were widespread much earlier than we think now, and there's just no record of them. They could even have originated in Gondwana and spread out from there. Placentals, suggest the Riches, might even have become extinct with the dinosaurs in Australia, making room for the marsupials to move in later.
Rich himself concedes, "Most radical ideas are wrong. It's wise to be wary of them—especially when they are your own. Even more radical to many paleontologists has been the marriage of plate tectonics evidence and the placental family tree proposed by evolutionary geneticist Mark Springer and his colleagues. Springer is part of a new generation of researchers who examine the strands of an animal's DNA rather than scraping dirt from fossils at a dig.
These molecular biologists read the sequences of genes in a living animal's DNA like an evolutionary history book. The scientists can then determine how closely these animals are related genetically and how long ago their ancestors diverged.
Troubling as it is to many paleontologists, Springer's reading of mammals' genetic history fits remarkably well with what geologists now know about the breaking up and subsequent motion of ancient continents. The oldest group of living placental mammals, according to Springer and his colleagues, arose in Africa just before the continent finished breaking away from the rest of Gondwana around million years ago.
Springer calls these animals afrotheres. They include elephants, aardvarks, manatees, and hyraxes. When Africa floated off, it carried these animals away to evolve on their own for tens of millions of years. The fossil record for Africa from this period is almost blank. Nevertheless, Emmanuel Gheerbrant, a researcher for the National Center for Scientific Research in France, speculates that Africa "must have been a laboratory for some very peculiar animals.
One species Gheerbrant has discovered from this period in Africa is the oldest and most primitive known member of the elephant group, the proboscideans.
The million-year-old fossil of Phosphatherium escuilliei was discovered in Morocco. It was the size of a fox, and although it lacked a trunk, it had many dental and cranial features strikingly similar to modern elephants. Paleontologists had long thought elephants were one of the younger modern groups, evolving from ungulates that originated in Asia. But Gheerbrant's fossil, like the genetic evidence, suggests that proboscideans are in fact one of the oldest of the modern ungulate mammals.
Today hyraxes resemble guinea pigs. But 35 million years ago hyraxes took many forms. Some were the size of rhinoceroses; others had long legs like gazelles. Most mammals on the African ark began to disappear around 20 million years ago, after Africa came into contact with the rest of the world again. But Africa wasn't the only ark. An ancient seaway split South America from Eurasia and North America for millions of years, and South America became home to what geneticist Springer calls xenarthrans, another group of placental mammals.
South America's fossil record during its isolation is far better than Africa's, and includes such xenarthrans as sloths, armadillos, and anteaters. Springer's data, in other words, indicate that the most recent common ancestor of placental mammals is Gondwanan. Contrary to more than a century of northern chauvinism, the northern continents have the youngest placental mammals. One group, the laurasiatheres, includes seals, cows, horses, whales, and hedgehogs. The other group, euarchontoglires, includes rodents, tree shrews, monkeys, and humans.
These genetic findings reveal more than simply which came first. They also redefine relationships among placental mammals. For one, anatomists have always assumed that bats were in the same superorder as tree shrews, flying lemurs, and primates. But genetic data place bats with pigs, cows, cats, horses, and whales. The data further show that these superorders of living mammals started to diversify much earlier than the fossil record suggests.
What gets fossilized is a record of an animal's shape. But geneticists contend that genes in an organism's mitochondria, the parts of a cell that are used to trace and date lineages, can be evolving rapidly without changing what would be left behind in the fossil record. Birds have a slow rate, yet they can evolve physically very rapidly.
However surprising the claims of geneticists seem at first, paleontologists and DNA researchers are finding that their theories can be complementary.
Some stunning new fossils have confirmed a previously controversial DNA finding about whales. Most paleontologists long believed that whales and dolphins—or cetaceans—descended from an extinct line of carnivorous mammals that for unknown reasons became aquatic between 50 and 45 million years ago.
At the time of these fossils' discovery, molecular biologists were maintaining that new DNA work indicated the cetaceans were actually aligned closely with artiodactyls, an order that includes even-toed ungulates such as pigs, camels, deer, and hippopotamuses.
Paleontologists first dismissed this unlikely connection because nothing in the fossil record supported it. Then in September two teams of fossil hunters published finds that backed up the claims of the biologists. A group led by Hans Thewissen of Northeastern Ohio Universities College of Medicine found two species of the earliest known whales in million-year-old deposits in Pakistan. Both had ear bones unique to whales, but the legs and anklebones of artiodactyls.
Almost simultaneously, a group from the University of Michigan led by Philip Gingerich announced similar fossils from Pakistan that had the same dual traits. The evolutionary transition among major groups of mammals is rarely illustrated so clearly.
And no other discoveries have linked fossils to DNA findings with such precision. Until 65 million years ago dinosaurs dominated the land. The oceans swarmed with huge sharks and voracious marine reptiles. The dinosaurs and other large predators occupied the richest and most obvious evolutionary niches, keeping mammals at the margins. Then an event occurred whose scale is still hard to comprehend.
An object six miles 9. That impact may have been one of many over the next several hundred thousand years, each adding to the destruction. The temperature reached degrees in parts of the world. They suddenly found themselves in a world without large carnivores.
Restraints were off. Within , years they were diversifying and growing bigger. Still, the majority of mammals didn't get much larger than a pig until the Eocene epoch, which began about 55 million years ago.
Then a rapid increase in global temperature encouraged the spread of forests around the world—even near both Poles. This abundance of rich vegetation opened yet more ecological niches for mammals to exploit. Mammal diversity soared. One of the newcomers in the fossil record was our own order, the primates. The earliest primates belonged to the lemur branch. Today lemurs are confined to the island of Madagascar, where one species made it from Africa perhaps 50 million years ago, probably on rafts of storm-tossed debris.
A few million years later, more advanced primates appear in the fossil record of eastern Asia. These higher primates are anthropoids—monkeys, apes, and humans. Chris Beard, a specialist in primate origins at the Carnegie Museum of Natural History, has unearthed in China what may be the earliest known example, called Eosimias.
These creatures evolved in the mid-Eocene as the world was cooling and concentrated in the midlatitudes where forests remained lush. Beard says they "must have been frenetic little animals.
Kind of caffeinated. They probably ate all the time. When you are that small, you have to. They probably lived in troops and maybe never left the tree they were born in. About 34 million years ago smarter, bigger, and more aggressive monkeys evolved. Catopithecus, one of many anthropoids his team has uncovered, has a skull the size of a small monkey's, a relatively flat face, and a bony enclosure at the rear of its eye sockets.
It is the first anthropoid to show the same arrangement of teeth humans have—two incisors, one canine, two premolars, and three molars—leading Simons to argue, "This is the first chapter of human history. At the start of the long Miocene epoch— The world was warming again and more seasonal climate patterns may have emerged. At higher latitudes, forests gradually gave way in many places to grassland meadows and savannas.
Because grass is abrasive, some mammals developed new dentition. Horses, for instance, emerged as little leaf-eaters in the forests but later developed molars that are much better adapted to eating grass. They physically resembled modern crocodiles and likely filled a similar ecological role. Between and million years ago, the first ichthyosaurs took to the seas, a group which would eventually dominate the oceans.
The origin of this successful group of marine reptiles is still not resolved. While the tuatara may look like a lizard, they are from a distinct lineage known as the sphenodonts. Around the same time that ichthyosaurs took the plunge, the first sphenodonts appeared. Represented today by just a single species - the tuatara - they are the sister group to lizards and snakes.
While they look very much like lizards they are in fact a distinct lineage. They were more diverse than the ancestors of modern lizards during the Triassic, performing similar ecological roles that lizards do today. The archosaurs were a component of the diapsid lineage, which includes many successful Mesozoic groups such as the dinosaurs and birds , pterosaurs , crocodilians and turtles.
By the Late Triassic there was a shift in dominance between the mammal-like reptiles and the archosaurs. There are various theories as to what may have caused this, such as competition in a climate that was becoming steadily warmer and dryer or evolutionary stagnation.
It seems that archosaurs were better able to fill the empty niches left following the extinction of some of the synapsid linages. Drepanosaurs were truely strange animals, and even today no one is quite sure where exactly they fit on the evolutionary tree.
The neck of Tanystropheus was extraordinarily long, equal to the length of its body and tail combined. Others included the incredibly long-necked Tanystropheus and, potentially, the bizarre chameleon-like drepanosaurs, which had a claw on the end of their tails. Another successful group was the phytosaurs. These animals looked quite crocodilian, but were from a different branch of the archosaurian tree.
The lineage that would give rise to the crocodiles was instead represented in the Triassic by much smaller, more gracile animals.
It was around million years ago that the first dinosaurs appear in the fossil record. These dinosaurs were small, bipedal creatures that would have darted across the variable landscape. The environment during the Triassic was as varied as it is today, with large swathes of forests, dry deserts and open prairies. There would likely have been an extremely arid interior, but also some very moist and wet temperate and tropical environments too. While reptiles were already dominating the oceans and the land, they also took the skies.
By million years ago, the first pterosaurs appeared, making them the earliest vertebrates to evolve powered flight. They would eventually evolve into extraordinary animals with a wingspan of over 15 metres, but the first pterosaurs were much more modest in size with long jaws and tails. Even though the archosaurs had managed to usurp the synapsids, some still clung on. By million years ago, one branch gave rise to the mammaliaformes, which were likely small, nocturnal insectivores.
It is from this group that the mammals would later emerge. While the non-dinosaurian archosaurs continued to dominate most environments, the dinosaurs rapidly started to diversify. Not long after they first appeared, the dinosaurs may have already diverged into two main groups. These were the Saurischia, which includes the sauropods, and the Ornithoscelida, which includes the theropods and ornithischians.
By the end of the Triassic, some of these early dinosaurs were impressive in size. A few of the first relatives of sauropods, such as Riojasaurus and Lessemsaurus , had already reached over nine metres in length.
The climate started to change so that by
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