What are mass extinctions?

We know what extinction is: the complete and permanent loss of a species. This kind of thing is happening all the time on Earth; it’s just part of how our planet works. While it’s always sad to see a unique form of life go, the losses are usually balanced out by the appearance of new species, as organisms continue to evolve and change.

Sometimes, though, an unusually large number of extinctions happen in a relatively short period of time, in an event known as a mass extinction. Though there’s no exact definition for what counts as a mass extinction, it’s generally agreed that there have been five really big ones in the past 450 million years of our planet’s history.

The largest of these, the Permian-Triassic event, killed over 90% of the species that were living on Earth at that time. It was this massive disappearance of life that paved the way for the rise of the dinosaurs.

Because the dinosaurs are the most famous of the former inhabitants of our planet, the event that killed them – the Cretaceous-Paleogene event – is the most famous of the mass extinctions.

Scientists are still unsure what caused these relatively-sudden waves of extinction. Possible causes include naturally-occurring climate change; geological events, like volcanic eruptions; disasters originating in space, like asteroid strikes; and, in the case of the more recent extinction events, hunting by early humans.

Many scientists agree, though, that we are witnessing a major extinction event right now. The Holocene extinction has been going on since 1900, with species vanishing 1,000 times faster than they normally do. Scientists likewise agree that this is due to human activity, including human-caused climate change; deliberate killing of animals through overhunting and overfishing; widespread destruction of habitat; and introduction of non-native species, which can overwhelm and outcompete species that haven’t met them before.

This enormous loss of diversity on our planet is sad, and it is avoidable, if we choose to take action. If we choose to do nothing, the results may be catastrophic. Because of the complex ways in which we rely on other forms of life, experts say that if we continue to lose species at the current rate, we ourselves are likely to be one of the casualties.

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What are mass extinctions?

How many species are there?

Kingdom phylum class order family genus species. Maybe you remember learning in some long-ago biology class that these seven categories are how we describe and identify every living thing on Earth.

Animalia chordata mammalia primates hominidae homo sapiens. That’s us: humans. Within the great tree of life, we are pretty odd; we are the only member of our genus. Put in terms of a family tree, it’s kind of like not having any siblings.

Even if you look at our extended family – our cousins – we’re pretty unusual. Our planet is home to just 5,400 or so kinds of mammals. (Though the discovery of new mammals is not as rare as many people think. The past decade has seen new types of shrews, bats, and dolphins – and even a few monkeys and apes – welcomed onto the list of mammals known to science.)

In comparison, there are nearly twice as many kinds of birds – birding checklists typically include over 9,000 recognized species. And there are about 31,000 known kinds of fish.

The plant kingdom boasts some 310,000 members, from mosses to grasses to shrubs to towering trees. It’s not unusual for a dedicated natural gardener to have hundreds of kinds of plants in their yard, with many or all of them being native species. It’s not just that there are a lot of species of plants in the world; a lot of species of plants are able to coexist within small areas.

The total number of plant species is still dwarfed by the total number of animal species, though, for one reason: beetles are a staggeringly prolific family, with over 360,000 species discovered, and many more likely waiting to be found.

If you lined up one representative of every species on Earth, fully one fifth of the creatures before you would be beetles. Only one would look like us.

All told, we share our planet with at least 1,899,000 other species, each of them living in their own way and making their own unique contribution to the amazing diversity of life on Earth. When we are able to see ourselves as just one out of many, we can find the grace and humility to share our world with all of our relatives.

How many species are there?

What’s new in natural yards? February 2019

Almost two years ago, That Blog reported that the rusty-patched bumble bee had recently been added to the endangered species list. Now, there’s a happy update: in 2018, more of the bees were seen in more places than in 2017, a year which itself had increased sightings as compared to 2016.

It’s important to remember that the seeming increase in the bee’s numbers and range might be because scientists are working harder to find it. However, it’s also true that the Endangered Species Act has successfully protected 99% of the species that have been added to it.

It is well within our power to save species from extinction, when we choose to do so. If we simply plant a variety of flowers in our yards, leave a little bit of bare soil, and refrain from spraying pesticides, we have created a new area of habitat for rusty-patched bumble bees. Every person who does this contributes to the continued existence of an animal that used to be common in our country.

This spring, make a mindful choice about what you want to pursue: a picture-perfect lawn, or a planet that thrives with wondrous biodiversity.

What’s new in natural yards? February 2019

What is an umbrella species?

Plants and animals are in big trouble. All over the world, wild species are vanishing, becoming first rare and then extinct, at an unprecedented speed. As a matter of our own survival, it is crucial that we begin to turn this around. But amid all this loss of life, even a committed conservationist might be defeated by the question: Where should we start?

In other words, what should we protect first? We might start with species that are known to be of great usefulness to humans, like pollinators. We might start with species we find awe-inspiring, like tigers and giant sequoias. We could start with the species that are in most imminent danger of extinction, or we could write off these vanishing creatures as lost causes and start with the species that we still have a real chance of saving.

Another idea is to start with umbrella species.

Here’s how it works: First, we identify a species that requires a large range, that has a wide variety of needs, that lives in an area packed with other kinds of life, or that is easy to rally support for. Then, we protect that species. In doing so, we go a long way towards also protecting all the species that live in the same area, that rely on similar resources, or that are closely connected to the species getting the special protection. The species that is directly being protected is called the umbrella species, because it acts as an umbrella, or a shield, for other plants and animals.

The umbrella species approach has some advantages. First, it’s easier to create and enforce a conservation plan for a single, well-studied plant or animal than to try to do the same for the hundreds or even thousands of species that are actually living in a given area. Second, it can be easier to build the political will to protect one iconic species – like whales or polar bears or Joshua trees – than to rally people to demand action to save the salamanders and the beetles and the pupfishes and the mosses and every other kind of living thing.

On the other hand, the strategy of focusing on a single species – usually a large mammal – can reinforce the idea that less majestic creatures are not important or not worth protecting in their own right. And, while protecting smaller creatures through protecting their umbrella species is better than not protecting them at all, it’s likely to be less effective than enacting conservation plans specifically tailored to each species.

How we think about this question influences how we garden in our yards. If we decide that we want to focus on protecting monarchs, all we really need to plant is milkweed. But that doesn’t do much to help other species. If we also want to protect swallowtails and fritillaries and atalas and commas and mourning cloaks, we need to plant pipevines and violets and coontie and elm trees and willows. Then we’re starting to build a thriving ecosystem that makes room for lots of other species as well.

What is an umbrella species?