extinction risk

Return of the frogs

September 22, 2025 By EarthWise Leave a Comment

The mountain yellow-legged frog is a species that lives in the mountains of Southern California. It is listed as an endangered species for protection by the federal government. Surveys 20 years ago determined that the frog’s population was declining and on a trajectory toward extinction. The frogs are severely impacted by water pollution and are vulnerable to the effects of wildfires, floods, disease, and drought.

A collaboration headed by the Scripps Institution of Oceanography at UC San Diego along with the San Diego Zoo Wildlife Alliance, UCLA, and the Big Bear Alpine Zoo has been raising mountain yellow-legged frogs in captivity as part of a long-running recovery program with partners at multiple federal and California state agencies.

In August, more than 350 of the frogs were reintroduced into the wild in Southern California’s San Bernardino Mountains, one of the largest releases of the captive-raised frogs to date. This represented the first species reintroduction by the Scripps Institution and an important milestone in its growing conservation work.

The frogs were transported in coolers to the mountains where a team then hiked the frogs to three sites along a lake within a protected reserve. The frogs were microchipped with passive transponder tags that will allow researchers to identify individuals during future surveys. This will enhance long-term monitoring and inform ongoing conservation efforts.

The goal of these efforts is to help to delist or at least downlist the endangered status of the frogs by enhancing the genetic diversity of both captive and wild populations, optimizing reintroduction efforts, and increasing wild frog populations.

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Hundreds of Mountain Yellow-legged Frogs Leap Back Into the Wild

Photo, posted April 27, 2011, courtesy of Rick Kuyper / USFWS via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Shrinking Birds | Earth Wise

June 5, 2023 By EarthWise Leave a Comment

A new study by researchers at Yale University looks at the way bird morphology is changing in response to the warming climate. As temperatures rise, birds’ bodies are growing smaller, but their wings are growing longer.

In the study, published in the Proceedings of the National Academy of Sciences, the scientists analyzed two independently collected datasets containing 40 years of morphology changes in 129 bird species comprising 52 migratory species in North America and 77 South American species.

In both datasets, similar changes were observed over the 40-year period. The overall trend makes sense given that being smaller and having longer wings both would help birds to stay cool in warmer weather. What was less obvious was that the changes to the birds were much greater among the smallest bird species.

One possible explanation is that smaller species tend to reproduce on a shorter time scale and therefore evolve more quickly. However, the study found no link between generation length and the changes in body size.

Another possible explanation is that smaller species tend to have larger populations, which means there is a greater chance of having individuals with desirable new traits that can get passed on. But the scientists found no link between population size and shifts in body size either.

At this point, it is unclear why smaller birds are shrinking more. More research is needed to figure out why larger birds are slower to adapt to climate change. In general, larger species of animals have an increased risk of extinction. This new research suggests that larger body size exacerbates extinction risk by limiting the ability for birds to adapt to the changes we are making to the climate.

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Birds Are Shrinking as the Climate Warms — and Small Birds Are Shrinking Faster

Photo, posted October 30, 2018, courtesy of N. Lewis / National Park Service via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Assessing The Planet’s Most Unique Birds | Earth Wise

January 11, 2023 By EarthWise Leave a Comment

Birds come in a huge variety of shapes, sizes and plumages. The physical attributes of birds are adaptations that have taken countless millennia to develop, and physical attributes are closely related to the roles birds play in their environment.

According to a new study led by researchers from the University College London in the U.K., bird species with extreme or uncommon combinations of traits have the highest risk of extinction. Losing these bird species and the unique roles they play in the environment, including seed dispersal, pollination and predation, could have severe consequences on the health of ecosystems.

In the study, which was recently published in the British Ecological Society journal Functional Ecology, the researchers analyzed the extinction risk and physical attributes of 99% of all living bird species. The research team used a dataset of measurements collected from living birds and museum specimens. The measurements included things like beak size and shape, and the length of wings, tails and legs. The researchers combined this data with extinction risk, and then ran simulations to see what would happen if the most threatened birds were to go extinct.

Some of the bird species that are both most unique and most threatened include the Christmas Frigatebird and the Bristle-thighed Curlew. Kiwis were excluded from the study because the researchers viewed them as extreme morphological outliers.

While most unique birds were also classified as threatened on the Red List, the research was unable to show what links uniqueness in birds to extinction risk

The research team warns that if more isn’t done to protect these threatened species and avoid extinctions, the functioning of ecosystems will be dramatically disrupted.

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Planet’s most unique birds at higher risk of extinction

Photo, posted June 25, 2012, courtesy of Kristine Sowl / USFWS via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

What Is An Endangered Species? | Earth Wise

March 3, 2020 By EarthWise Leave a Comment

Biodiversity is declining rapidly throughout the world and people are mostly the reason. Species are disappearing because of changes in land and sea use, the direct exploitation of organisms, climate change, pollution, and invasive alien species resulting from globalization. The challenges of conserving the world’s species are many and difficult. Among these challenges are determining which species are endangered and how and when to protect them.

What constitutes an endangered species is not necessarily obvious.

Extinction risk increases as a species is driven to extinction from portions of its natural range. Most mammal species have already been driven to extinction from half or more of their historic ranges because of human activities.

According to a recent survey of ordinary Americans, three-quarters of participants said that a species deserves special protections if it had been driven to extinction from any more than 30% of its historic range. This compares with the language of the U.S. Endangered Species Act that defines an endangered species as one that is “in danger of extinction throughout all or a significant portion of its range.”

Experts and decision-makers are more accepting of risks and losses because they believe greater protection would be impossibly expensive. Decision-makers tend to be influenced by special interest groups with a vested interest in not instituting protections.

Before human activities began elevating extinction risk, a typical vertebrate species would have experienced an extinction risk of 1% over a 10,000-year period. Current policies consider a 5% risk over 100 years to be acceptable. Policies consider whether we can afford to protect species. Given the dangers of declining biodiversity, we should ask whether we can afford not to.

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What Is An Endangered Species?

Photo, posted July 29, 2018, courtesy of Sergio Boscaino via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.