‘What are the consequences that have been observed in Mexico due to climate change?’ » Yale Climate Connections

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One of our readers asked us:

What are the consequences that have been observed in Mexico due to climate change? I would like to know what types of animals, species, or plants have been going extinct in recent years in Mexico.

We asked YCC contributor Tree Meinch, who is based in La Paz, México, to help us answer this question. This is what they found:

In the world of species conservation, ‘‘extinction” is a slippery fish.

For starters, how does anyone know when a particular species has officially disappeared from the face of our planet? To claim this with confidence, you have to turn over a lot of rocks, both literal and figurative ones.

In the more common scenario, where we know a species is declining, a whole web of scientific disciplines must evaluate the contributing factors. There are typically many of them, including changes in our climate.

Coral has become one hallmark indicator of climate change in our oceans due to the close association between rapidly warming oceans and major bleaching events that cause mass die-offs. And we recently learned that our oceans are warming at twice the rate they were just 20 years ago.

This rapid shift poses major hurdles for even the most adaptable plants and animals.

“The problem with climate change and other human activities is the animals can’t change fast enough. They need hundreds and thousands of years to adapt to conditions,” said Gerardo Ceballos, a long-time researcher with the Institute of Ecology at the Universidad Nacional Autónoma de México.

In the case of staghorn coral, it’s now listed as critically endangered in Mexico. That’s based on an inferred population decline of more than 80% in just 30 years, according to a comprehensive assessment in 2021.

The pace of environmental changes today as a result of human activity has sparked what many scientists call the sixth mass extinction for our planet.

This sobering reality informed Ceballos’ latest coauthored book, “Before They Vanish,” released by Johns Hopkins University Press this fall.

The threat of the changing climate carries particularly high stakes for Mexico, given its reputation as a “megadiverse country” claiming nearly 10% of the world’s biodiversity, according to one 2019 study.

When we speak of species extinction and endangerment, the prevailing global authority is the International Union for the Conservation of Nature, commonly known as the IUCN. The organization maintains the Red List of threatened species, with categories such as “near threatened,” “critically endangered,” and “extinct in the wild” preceding “extinct.”

That final designation often lands at the end of a long domino train of questions, inquiry and escalated concern.

With that in mind, nearly 50 species today are officially designated as “probably extinct” in Mexico, according to one federal database. This includes the San Quintin kangaroo rat, multiple species of warblers, the Caribbean monk seal, and even grizzly bears.

Ultimately, zeroing in on complete extinction can be a distraction – and a costly one at that – in the conservation field, according to Ceballos. Sometimes you also get a surprise reappearance of a supposedly extinct species, as was the case for Mexico’s kangaroo rat 30 years after the last reported sighting.

“If we focus only on species extinction, we’re missing the point,” Ceballos said. “What is alarming now is the rate of individuals disappearing, and the rate of populations declining.”

The Red List flags nearly 500 species in Mexico as “critically endangered” and less than 30 as extinct.

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

Ceballos can rattle off a list of large megafauna alone that have mostly or completely disappeared from Mexico at some point in the past 100 years. This includes the gray wolf, grizzly bears, bison, and elk – though some of these animals have since been reintroduced to parts of Mexico from other global populations.

To be clear, many of the population die-offs above are related to excessive hunting or poaching, deforestation, and in some instances mass poisoning – even organized strategically by U.S. government officials in the case of the Mexican gray wolf. Factors like habitat loss often involve climate change or other human developments and land modification.

Still, the climate has always been and remains a constant factor influencing the behaviors and success of species. We also know that regional temperature swings, drought, unpredictable extreme weather events and habitat loss are on the rise.

Quantifying the toll of climate change in each instance of species decline is its own complicated affair beyond surveying population counts. Specialists across the fields of biology, ecology, and oceanography are dedicated to that pursuit, examining indicators like sudden migration shifts and decreased species sightings.

Research expenses and the vast number of variables make for slow, painstaking progress when connecting the dots between climate variables and species impact.

Things grow more challenging and costly in ocean ecosystems, according to oceanographer Elva Escobar Briones, a specialist in deep sea diversity and conservation in Mexico.

“The effect of noise pollution, plastic pollution, or dissolved compounds derived from anthropogenic activities is poorly documented,” Escobar Briones said.

The same goes for our understanding of beach erosion and its effect on turtles or the intricate consequences of ocean acidification and thermal stratification for sea life. We know rising sea temperature has an impact on many things, but the details are fuzzy and context-dependent.

The disappearance of the vaquita, a cartoonish-looking small porpoise endemic to the upper Gulf of California, has been one of the most widely-recognized extinction events unfolding in real time. Yet in this case, hazardous gill nets and illegal fishing practices have posed the primary threat to these creatures.

Beyond the fishing industry, Mexico’s biodiversity is also closely tied to a booming tourism industry, agriculture operations, and other human forces delivering a ripple effect of change.

“If we continue this path, we will lose many species,” Ceballos said. “And it hasn’t hit animals and plants full-scale yet.”

In one splash of hope, national officials reintroduced the American bison to parts of Mexico in the past few years. Their return could help fight the impacts of climate change, since they are deemed an umbrella species that supports a whole chain of plants and animals within their ecosystem.

This reintroduction effort demonstrates the positive side of how a keystone species can quickly improve diversity of habitat and life for the better, amid many mounting challenges in our rapidly changing world.