“What consequences of climate change are observed in Mexico?” » Yale Climate Connection

A reader asked us:

What consequences of climate change are observed in Mexico? I would like to know what types of animals, species or plants are becoming extinct in Mexico in recent years.

We asked YCC writer Tree Meinch, based in La Paz, Mexico, to help us answer this question. Here's what they found:

In the field of species conservation, “extinction” is a slippery fish.

For starters, how to Know When a particular species officially disappears from the face of our planet? To confidently claim this, you have to turn over a lot of rocks, both literally and figuratively.

In the more common situation where we know a species is in decline, an entire network of scientific disciplines must assess the contributing factors. Often there are many, including changes in our climate.

Corals have become one of the hallmarks of ocean climate change due to the strong link between rapid ocean warming and major bleaching events that cause mass die-offs. We recently learned that the ocean is warming twice as fast as it did 20 years ago.

This rapid transformation poses a major obstacle to even the most adaptable plants and animals.

“The problem with climate change and other human activities is that animals don't change fast enough. They need hundreds or thousands of years to adapt,” said Gerardo Ceballos, a long-time researcher at the Institute of Ecology at the National Autonomous University of Mexico. Ceballos said.

In the case of Acropora, it is now listed as critically endangered in Mexico. This is based on an extrapolation of a population decline of more than 80% in just 30 years, based on the 2021 Comprehensive Assessment.

Today, the rate of environmental change caused by human activities has triggered what many scientists call Earth's sixth mass extinction.

This sobering reality informs Ceballos’ latest co-authored book, “Before They Disappear,” published this fall by Johns Hopkins University Press.

According to a 2019 study, the threat of climate change is particularly important for Mexico because Mexico is known as a “biodiversity powerhouse” and has nearly 10% of the world's biodiversity.

When we talk about species extinction and endangerment, the most authoritative body in the world is the International Union for Conservation of Nature, commonly known as IUCN. The organization maintains a red list of threatened species, which includes categories such as “near threatened,” “critically endangered” and “extinct in the wild.”

The final designation often comes at the end of a domino of questions, inquiries and escalating concerns.

With that in mind, nearly 50 species in Mexico are now officially designated as “possibly extinct,” according to a federal database. These include San Quentin's kangaroos, several species of warblers, Caribbean monk seals, and even grizzly bears.

Ultimately, Ceballos said, in the conservation field, focusing on total extinction can be distracting and costly. Sometimes you're also surprised to see a species thought to be extinct reappear, as was the case with the Mexican kangaroo 30 years after the last reported sighting.

“If we only focus on extinction, we're missing the point,” Ceballos said. “The concern now is the rate at which individuals are disappearing and the rate at which populations are declining.”

The Red List labels nearly 500 species in Mexico as “critically endangered,” with fewer than 30 species marked as extinct.

In 2020, a groundbreaking study, including by IUCN, revealed that more than one-third of Mexico's freshwater fish species are threatened with extinction.

Ceballos can rattle off a list of large megafauna that have mostly or completely disappeared from Mexico at some point in the past 100 years. These include gray wolves, grizzly bears, bison and elk – although some of these animals were later reintroduced to parts of Mexico from other groups around the world.

To be clear, many of the population deaths mentioned above are linked to overhunting or poaching, deforestation, and in some cases mass poisoning—even, in the case of the Mexican gray wolf, strategically organized by U.S. government officials. Factors such as habitat loss often involve climate change or other human development and land modification.

Nonetheless, climate has always been and remains a constant factor in species behavior and success. We also know that regional temperature swings, droughts, unpredictable extreme weather events and habitat loss are increasing.

Beyond surveying human populations, quantifying the costs of climate change each time a species declines is a complex matter in itself. Experts in the fields of biology, ecology and oceanography devote themselves to this pursuit, studying indicators such as sudden migration changes and species declines.

Research costs and the multitude of variables make progress slow and painstaking when it comes to linking climate variables and species impacts.

Elva Escobar Briones, an oceanographer and expert in deep-sea diversity and conservation in Mexico, said the situation has become more challenging and costly for marine ecosystems.

“The effects of noise pollution, plastic pollution, or dissolved compounds from human activities are poorly documented,” Escobar Briones said.

The same goes for our understanding of beach erosion and its impact on sea turtles, or the complex consequences of ocean acidification and thermal stratification on marine life. We know that rising sea temperatures will affect many things, but the details are fuzzy and depend on the circumstances.

The disappearance of the vaquita, a small, cartoonish porpoise that lives in the upper Gulf of California, is one of the most widely recognized instant extinction events. In this case, however, dangerous gillnets and illegal fishing practices pose a major threat to these creatures.

Beyond fisheries, Mexico's biodiversity is closely tied to booming tourism, agricultural operations and other human resources that create ripple effects of change.

“If we continue on this path, we will lose many species,” Ceballos said. “And it hasn't fully affected flora and fauna yet.”

In the past few years, state officials have reintroduced bison into parts of Mexico, providing a glimmer of hope. Their return could help combat the effects of climate change, as they are considered an umbrella species that supports the entire chain of flora and fauna within their ecosystems.

This reintroduction effort shows the positive side of how keystone species can quickly improve the diversity of habitats and life for the better in a rapidly changing world facing many growing challenges.