Editor's note: Interviews have been edited for length and clarity. Participants:

• Evolutionary Biologist Dr. Shane Campbell-Staton: Host and narrator.

• Evolutionary and Behavioral Ecologist Dr. Robin Tinghitella: Researches pacific field crickets.

• Ecologist and Climate Change Expert Camille Parmesan: Researches Edith’s checkerspot butterflies.

• Behavioral Ecologist Dr. Mylene Mariette: Researches zebra finches.

• billy barr: Recorded observations of broad-tailed hummingbirds.

billy

“Any time you get substantial environmental changes, they will affect almost everything. Hummingbirds migrate from their wintering location, and where they’re coming from may not have much to do with the conditions here — so they can return here into a surprise situation.

“In most recent years, the snow has melted away and plants started growing sooner than they might have historically. This can affect what food sources are available for the birds when they arrive, and also the general habitat. They might settle in and start nesting earlier only to get hit by what once was a typical snowstorm in June — but now they’re further along with their young, and keeping them fed and warm would be difficult.

“There are other adjustments hummingbirds have to make, too. For example, other species come into this area that were not here before. We never had crows out here, but now they nest in large groups and are predators to hummingbird chicks.”

Mylene

“The zebra finch is doing well compared to many other species, but it is already starting to be impacted by climate change. In parts of Australia, such as the Northwest, where temperatures have increased the most since the 20th century, the zebra finch has already disappeared in summer.

“Extremely hot days (45ºC and above) used to be very rare, but their frequency has increased a lot in the last 10 years, including at my field site. At these temperatures, the birds are no longer able to keep their body temperature down. A huge number of individuals die of dehydration or overheating.”

Camille

“The Edith's checkerspot butterfly has a complicated relationship with climate, and hence also with human-driven climate change. This is a butterfly that doesn't move around much — most individuals die within a hundred meters of where they were born. This stay-at-home behavior has allowed the butterflies to evolve a lot of ‘local adaptations,’ meaning that different populations are genetically adapted to live in particular habitats and feed on particular plants. As a result, some populations are very sensitive to certain climate extremes. These populations have suffered a very high local extinction rate with recent increases in droughts, fires and heat waves that are all a part of climate change. But other populations, with different ecologies — different local adaptations — are quite resilient.

“In general, populations at the highest elevations (in the Sierra Nevada) and furthest North (in Canada) are doing well, while those in naturally hotter and drier regions (southern California, lower elevations in California and Nevada) are doing poorly, with many populations having gone extinct in the past 30 years.”

Shane

“In our modern world, humans have become about as big of an influence on the Tree of Life as anything else in Earth’s past. We are impacting every corner of the globe in some way; even the farthest, most uninhabited reaches of our planet are not safe from our influence. The current age of life is literally defined by our impact: The Anthropocene – The Age of Humans.

“We’re already seeing the consequences play out in real-time. Species are going extinct at an incredible rate, natural ecosystems worldwide are being uprooted for agriculture and urban development, species are being reshuffled around the globe (intentionally and unintentionally) and bringing new challenges for native species. We are throwing a lot at the living world all at once.”

Mylene

“Australia is becoming hotter and drier at an accelerating rate. The areas where zebra finches and other desert-adapted species can live will continue to shrink. Species with smaller ranges or less mobility than the zebra finch will likely go extinct. Whether adaptation can occur faster than climate change is a big and important question to which we only have the beginning of an answer.”

Camille

“As Earth warms, the areas that have a suitable climate for a given species shift geographically. For a species to maintain its experience of climate, its range must move poleward in latitude and upward in elevation.

“Back in 1996, my work on Edith's checkerspot butterflies provided the first clear example showing that this was already happening, for any species of plant or animal. The proportion of previously recorded populations of the checkerspot that were extinct in the 1990s was much lower in Canada than in Mexico and lower at high elevations than at low elevations. This pattern showed that some climate-sensitive populations had already been driven extinct by climate change, and others will surely follow. These were populations that failed to adapt to the changing climate in time to save themselves.”

billy

“Species that have evolved in specific niches will have more difficulty adapting to environmental change, while others will do better if they move into areas where it was once too cold. The most flexible species will adjust — even if it means some birds move to town in winter and feed from feeders rather than in their once ‘natural’ environment. Those that are fixed to certain environmental conditions may not survive.”

Robin

“I’ve personally studied rapid evolution in two different study systems: the Pacific field crickets highlighted in ‘Evolution Earth’ and a small fish called the threespine stickleback.

“Typically, male sticklebacks have shiny blue bodies and bright red throats that females just can’t get enough of. Females choose the males with the biggest, brightest red throats because the color indicates things like health and parasite resistance. When these fish invaded freshwater rivers and lakes in the northwest parts of North America about 10,000 years ago as glaciers retreated, they underwent all kinds of rapid evolutionary changes. That included physiological changes to deal with living in freshwater and even rapid and repeated evolutionary changes in body armor.

“I studied why and how freshwater stickleback in some locations lost the sexy red throat altogether, replacing it with black body coloration. It seems this was a response to differences in water color — where the fish are now black, the streams they live in are slow-moving and very tannic, and a bright red throat can’t be easily seen by female fish in red-stained water. Just like with the crickets, it’s interesting to think about why female stickleback are willing to accept males for mating when they don’t have that bright red throat.

“I think we’re likely to continue to see evolution happening on these incredibly fast timescales, especially given the pace of environmental and climate change that we’re causing.”

Shane

“Some species will adapt — we’re already seeing this. The species most likely to adapt will be small animals with large populations that can reproduce quickly. This will give natural selection a shot at reshaping life to keep pace with the changes we’re making to the planet.

“Larger species, in general, will have a harder time keeping pace with rapid change. Their relatively small population sizes, more expensive habitat needs and slow reproduction times leave them more vulnerable to population decline and extinction. The unfortunate thing is, those are the species people are most enamored by: gorillas, wolves, elephants, tigers, etc. If we don’t right the ship, those species are likely to be the first to be lost overboard.”

Robin

“Introduced and invasive species are a huge problem, particularly on islands. Hawaii has even been called the extinction capital of the world because invasive species have wreaked havoc on native organisms. More than 50% of native birds in Hawaii are estimated to have gone extinct, for instance.

“Sometimes people introduce non-native species intentionally, but often these organisms are accidental hitchhikers that catch a ride. There are many relatively simple things we can do to help, ranging from planting native plants in our home gardens rather than introduced ornamentals to keeping a watchful eye and reporting the presence of invasive species where they haven’t been seen before.”

Mylene

“Preserving habitat is at least as important as reducing climate change to stop the biodiversity crisis because habitat loss aggravates climate change and its impact. People can provide drinking and bathing water and thermally insulated nesting sites for birds. They can provide habitat for wildlife by having lusher gardens with more native plants, which also keep temperatures down; or they can mow the lawn less often so it provides seeds to birds and is more heat resilient.”

Camille

“The most important thing to do is to mitigate climate change itself. Reducing greenhouse gas emissions is a top priority, in all of the many ways that are possible: increasing the use of renewable energies, watching your household energy budget, buying more energy-efficient cars and trucks.

“But we also need to encourage the ability of nature to take up some of the excess carbon dioxide through ‘nature-based solutions.’ Restoring natural systems that have been stressed by invasive species, over-fertilized with run-off from farming and automobile exhaust, poisoned by toxic wastes from industry, pesticides and herbicides — returning them as much as possible to a healthy state of being — will actually also help them combat climate change.

“It's been shown that healthy ecosystems don't suffer as much as degraded ecosystems when a drought or heat wave comes along, so the species within those systems are buffered from the worst impacts. This won't save nature if we keep going as we are, but will do a lot to help as we head toward the 2°C warming that governments have agreed is the threshold for ‘dangerous’ climate change.”

billy

“People need to support policy-making decisions and the leaders who make them, which promote a cleaner environment. We can also purchase products that are safer with less negative impacts, and less packaged food — we need to be less of a throw-away society. Don’t leave lights on or windows open while the air conditioner or heater are on. Drive less; bike and use mass transit more. Conserve water instead of making green lawns in a desert. These are just a few of the many small decisions we make on a daily basis, but they add up.

“As for wildlife, we need to stop harassing them and think of how our actions can affect them, and sort of leave them alone. They should not be made dependent on people to survive. There needs to be ample open and undisturbed space. But the best way to help all living things is to strive for a more sensible way of living and to use fewer resources in doing so.”

Although “Evolution Earth” focuses on animal species you may never see in real life, remember that every single one of us is a star in the story of our changing world. No matter where you live or how you interact with your local environment, there’s always something you can do to make a more positive impact — even something as simple as learning more.

To take a closer look at these species and their stories, watch “Evolution Earth” on PBS.