Hatchling turtles are cute, small and inexpensive. Handled improperly, they also can make you sick.

Turtles are well-known carriers of salmonella, a common bacterial disease that causes fever, stomach cramps and dehydration and can lead to severe illness, especially in young children and elderly people. In August 2023, the Centers for Disease Control and Prevention released an advisory about an 11-state outbreak of salmonella bacteria linked to pet turtles.

“Don’t kiss or snuggle your turtle, and don’t eat or drink around it. This can spread Salmonella germs to your mouth and make you sick,” the agency warned.

Global trade in turtles is big business, and the U.S. is a leading source, destination and transit country. Some of this commerce is legal, some is not. For example, it has been illegal in the U.S. since 1975 to sell turtles with shells less than 4 inches (10 centimeters) in diameter because young children often contract salmonella from them. But it’s easy to find them for sale nonetheless.

However, humans are a much bigger threat to turtles than vice versa. Over half of the world’s turtle species are classified as threatened or endangered, and overharvesting of wild turtles is a major cause. Turtles also face other threats, including habitat loss, climate change, pollution, diseases, invasive species and death or injury while trying to cross roads.

As a conservation biologist, I work with colleagues from academia, nonprofit organizations and state and federal agencies to protect threatened species and combat wildlife trafficking. I also use the global wildlife trade to teach important ecological concepts and research skills. Here’s what we know about trade in turtles and how it threatens their survival.

Life in the slow lane

It’s hard to harvest turtles sustainably because they are so long-lived. Individual turtles of some species can survive for more than 100 years. Most turtles reach reproductive maturity late in life and have relatively few eggs, not all of which produce successful offspring.

To put this in context, compare a common female snapping turtle from the northern U.S. with a female white-tailed deer. Begin at the start of their lives and fast-forward 17 years. At this point, the snapping turtle will just be ready to reproduce for the first time; the deer will already be dead, but it may have produced over 600 descendants. It can take a female turtle her entire life to generate one or two offspring that in turn reach adulthood and replace her in the population.

Turtles are valuable because they play diverse roles in land, freshwater and ocean ecosystems. For example, tortoise burrows provide refuge for hundreds of other species, including birds, mice, snakes and rabbits. Box turtles – the type you may encounter in your garden – consume practically any kind of plant material and excrete the seeds as they move around, helping plants spread. Some seeds even germinate more readily after passing through a box turtle’s gut.

In lakes and ponds, freshwater turtles serve as both predator and prey, and they help maintain good water quality by consuming decaying organisms. Terrapins reside in brackish water zones, where rivers flow into oceans and bays, and feed heavily on snails. Without terrapins present, the snails would quickly consume all underwater seagrasses, which would harm fish, shellfish, sea urchins and other organisms that rely on seagrasses for their survival.

In global demand

Humans have long been fascinated with turtles. Revered in many cultures, turtles have symbolized strength and longevity for centuries. Today, people use turtles as pets; sources of food, jewelry and other curios; and in traditional medicines and religious and cultural practices.

International trade in turtles takes place on a massive scale. According to the U.S. Fish and Wildlife Service, nearly 127 million turtles were exported just from the U.S. between 2002 and 2012. About one-fifth (24 million) came from the wild.

More recent data indicates that exports declined between 2013 and 2018, but trade in particular species increased. Commercial freshwater turtle farming is still a multimillion-dollar industry in the southeastern U.S.; a small number of native turtle species, largely bred on turtle farms, now make up the bulk of legal U.S. exports, for use as both pets and food.

There’s no good way to quantify how many native turtles are harvested from the wild. But history shows what happens when they are hunted without limits. Historic demand for sea turtles, diamondback terrapins and snapping turtles as food led to such crashes in populations that management agencies had to regulate their harvesting.

Turtles also are gaining popularity as pets, particularly for younger adults. Surveys indicate that more than 2 million Americans own turtles. To curb pressure on wild populations, state agencies are prohibiting or limiting personal collection and possession of native turtles.

Black market turtles

Despite existing regulations, demand for some native North American turtle species is so strong that people collect, smuggle and sell the animals illegally. For example, in 2019 a Pennsylvania man was sentenced to six months in prison and fined $250,000 for trafficking thousands of protected diamondback terrapins.

Rare species such as wood turtles and Blanding’s turtles, as well as uniquely patterned individual turtles, command top value on the black market. Internet commerce, social media apps and online payment mechanisms make it easy for illegal buyers and sellers to connect.

Between 1998 and 2021, U.S. enforcement agencies intercepted at least 24,000 protected freshwater turtles and tortoises from 34 native species that were being illegally traded across the U.S. These animals may be held without food and water and in crowded spaces, sometimes wrapped in tape and stuffed in socks.

How to help

To curtail the illegal turtle trade, regulators are working to strengthen regulations and increase enforcement. Private citizens can also help reduce the demand and protect wild turtles. Here are some simple steps:

• Before you purchase any live animal or wildlife-related product, review relevant local, state, national and international regulations. Just because something is for sale doesn’t mean it’s legal.

• Make an informed decision about owning a turtle. Consider the size it will reach as an adult, its care requirements and its life span. Prioritize adopting one from a reputable rescue organization, and seek out a captive-bred turtle instead of a wild one.

• Don’t release an animal that you no longer want or can’t care for into the wild. This is illegal and can have serious ecological impacts. The red-eared slider (Trachemys scripta elegans), a freshwater turtle that’s native to the Mississippi River basin, was sold by the millions in recent decades and released by many pet owners. Now it is considered one of the world’s most invasive species because it outcompetes native turtles for food and space.

• If you encounter illegal wildlife collection, smuggling or sales, report them to your state fish and wildlife agency or the U.S. Fish and Wildlife Service for investigation.

• Support efforts to conserve and restore turtle habitat and minimize other threats, such as pollution and road traffic.

Jennifer Sevin is a co-founder and serves on the steering committee of the Collaborative to Combat the Illegal Trade in Turtles.

Radios crackle with chatter from a wildfire incident command post. Up the fireline, firefighters in yellow jerseys are swinging Pulaskis, axlike hand tools, to carve a fuel break into the land.

By 10 a.m., these firefighters have already hiked 3 miles up steep, uneven terrain and built nearly 1,200 feet of fireline.

It’s physically exhausting work and essential for protecting communities as wildfire risks rise in a warming world. Hotshot crews like this one, the U.S. Forest Service’s Lolo Hotshots, are the elite workforce of the forests. When they’re on the fireline, their bodies’ total daily energy demands can rival that of the cyclists in the Tour de France, as my team’s research with wildland fire crews shows.

These firefighters are also caught in Congress’ latest budget battle, where demands by far-right House members to slash federal spending could lead to a governmentwide shutdown after the fiscal year ends on Sept. 30, 2023.

After extreme fire seasons in 2020 and 2021, Congress funded a temporary bonus that boosted average U.S. Forest Service wildland firefighter pay by either 50% or US$20,000, whichever was lower. But that increase expires after Sept. 30, knocking many federal firefighters back to earning the minimum $15 per hour.

Legislation to make the raise permanent is pending before Congress, which is now preoccupied. A short-term pay boost may be possible, but that doesn’t solve the long-term pay problem. And if the government shuts down, federal firefighters will be working without immediate pay. The National Federation of Federal Employees warns that a large number of firefighters could quit if their pay also drops.

Firefighters push their bodies to extremes

Life on the fireline is demanding. Pack straps dig into the neck and shoulders with each swing of the Pulaski. It’s a constant reminder that everything wildland firefighters need, they carry – all day.

The critical water and food items, supplies, extra gear and fireline tools – Pulaskis, chain saws and fuel – add up to an average gear weight often exceeding 50 pounds.

Hiking with a load and digging firelines with hand tools burns about 6 to 14 calories per minute. Heart rates rise in response to an increased pace of digging.

Measured with the same techniques used to quantify the energy demands of Tour de France riders, wildland firefighters demonstrate an average total energy expenditure approaching 4,000 to 5,000 calories per day. Some days can exceed the Tour’s average of about 6,000 calories, equivalent to around 12 McDonald’s Happy Meals. Add to that a daily water need of 1.5 to over 2 gallons.

This isn’t just for a few days. Fire season in the western United States can last five months or more, with most Hotshot crews accumulating four to five times the number of operational days of the 22-day Tour de France and over 1,000 hours of overtime.

The physical demand of a day on the fireline

My team has been measuring the physical strain and total energy demands of work on an active wildfire, with the goal of finding ways to improve firefighter fueling strategies and health and safety on the line.

The crew members we work with are outfitted with a series of lightweight monitors that measure heart rate, as well as movement patterns and speed, using GPS. Each participant swallows a temperature-tracking sensor before breakfast that will record core body temperature each minute throughout the work shift.

As the work shift progresses, the Hotshots constantly monitor their surroundings and self-regulate their nutrient and fluid intake, knowing their shift could last 12 to 16 hours.

During intense activity in high heat, their fluid intake can increase to 32 ounces per hour or more.

The highest-intensity activity is generally during the early morning hike to the fireline. However, the metabolic demands can sharply increase if crews are forced into a rapid emergency evacuation from the fire.

My team’s research has found that the most effective way for wildland firefighters to stay fueled is to eat small meals frequently throughout the work shift, similar to the patterns perfected by riders in the Tour. This preserves cognitive health, helping firefighters stay focused and sharp for making potentially lifesaving decisions and keenly aware of their ever-dynamic surroundings, and boosts their work performance. It also helps slow the depletion of important muscle fuel.

Although crews gradually acclimatize to the heat over the season, the risk for heat exhaustion is ever present if the work rate is not kept in check. This cannot be prevented by simply drinking more water during long work shifts. However, regular breaks and having a strong aerobic capacity provides some protection by reducing heat stress and overall risk.

The season takes a toll

Hotshots are physically fit, and they train for the fire season just as many athletes train for their competition season. Most crew members are hired temporarily during the fire season – typically from May to October, but that’s expanding as the planet warms. And there are distinct fitness requirements for the job. The physical preparations are demanding, take months and are expected, even when temporary crew members are not officially employed by the agencies.

Still, with the immense physical demands of the job, crew members often experience a decay in metabolic and cardiovascular health and an increase in cholesterol, blood lipids and body fat. It is unclear why such a hardworking job often makes firefighters less healthy, requiring an off-season reset to recover, retrain and rebuild.

The season causes damage. This unfolds counter to the commonly accepted benefits of regular exercise. Pollutant and smoke exposure, lapses in nutrition, sleep disorders and chronic stress during the season seem to gradually poke holes in the Hotshot armor.

Progressive intervention strategies can help, such as educational programs on specific physical training and nutritional needs, mindfulness training to reduce the risk of job-oriented anxiety and depression, and emotional support for crew members and families. However, these require agency and congressional investment, a commitment beyond ensuring pay raises remain intact. Removing either is synonymous with taking away critical tools for the job on the firelines.

Developing offseason practices that pay close attention to both physical and mental health recovery can help limit harm to firefighters’ health. Many Hotshots have bounced back and returned season after season. However, a government shutdown and failure to act on pay for front-line fire crews could worsen crew retention in an already dwindling workforce.

This is an update to an article originally published Aug. 8, 2023.

Brent C. Ruby receives funding from a wide range of DOD agencies to study human performance during environmental stress.

Life exists in every conceivable environment on Earth, from the peaks of towering mountains to the remote stretches of isolated islands, from sunlit surfaces to the darkest depths of the oceans. Yet, this intricate tapestry of existence isn’t spread uniformly.

For centuries, scientists have marveled at the extraordinary variety of species exhibited in tropical regions. The breathtaking biodiversity of the Amazon rainforest, the teeming life in Madagascar’s unique ecosystems, the species-rich cloud forests of Costa Rica – the tropics showcase nature’s opulence.

What makes the tropics so incredibly diverse?

Since the dawn of biodiversity studies, scientists have believed the predominant factor is climate – the long-term patterns of temperature, precipitation and other atmospheric conditions. Thinkers like Alexander von Humboldt set the stage in the early 19th century with their keen observations, highlighting how life-rich regions often shared certain climatic features. Fast-forward to the present, and scientists confidently correlate climate with biodiversity. Simply put, hotter, wetter, resource-rich regions are veritable cradles of life.

Some climatic conditions spread across vast landscapes, while others appear fragmented, resembling isolated islands amid varying climates. This difference raises an intriguing question: Is an area’s biodiversity solely due to its climate? Or do the size and relative isolation of these climatic pockets influence the richness and abundance of species that thrive within them?

We are part of an international, interdisciplinary team interested in the puzzle of how the geography of climate and the global patterns of species diversity fit together. Geography of climate is a bigger part of the biodiversity picture than previously assumed, according to our study findings recently published in the journal Nature.

Unraveling the geography of climate

Historically, to study global biodiversity patterns, researchers divided the world into equal area grids and counted the species in each square.

Our study diverged from conventional methods. Instead of focusing solely on specific geographical locations, we centered our attention on the unique climate profiles of regions. Essentially, we weren’t just looking at plots on Earth but every place that shared a particular set of climatic conditions. We then classified these conditions globally and meticulously counted the species – birds, mammals, amphibians and reptiles – that live within the boundaries of each climate.

Central to our investigation was an exploration of the geography of these climates, examining both their size and isolation. Some climates are widespread and common, sprawling over vast areas. Others are more fragmented, emerging as isolated pockets amid different climatic zones, reminiscent of islands in a vast ocean of other diverse climates. Consider tropical climates: They cover vast expanses cumulatively, despite being broken up into smaller, unconnected bits, even on different continents.

Our findings were illuminating. Climate, of course, was an important factor in how many species flourished in a location. But we were intrigued to find that about a third of the variation we found in species diversity across the globe can be attributed solely to the size and degree of isolation of all the instances of a particular climate.

Biodiversity responds not just to the type of climate but its spatial distribution. Beyond the known effects of warmth and moisture, we found that larger and more isolated climates foster greater species diversity. Moreover, these expansive, broken-up climates not only housed a greater number of species but also nurtured a more unique combination of species.

By leveraging but transcending traditional methodologies, our approach unearthed novel insights about the geographical characteristics of climates. We discovered that the larger a climatic zone is, the more fragmented and scattered it tends to be across the landscape.

Isolation spurs diversity

Traditionally, scientists have thought of tropical climates as cohesive expanses, standing as barriers between the distinct extra-tropical climates of our planet’s poles. Our analysis confirmed that cooler extra-tropical climates are relatively well connected across much of the planet.

Yet, our findings reveal a different narrative for the tropics: Tropical climates appear more as fragmented islands amid a sea of diverse climates, rather than expansive, interconnected realms. Our revelation underscores that tropical climates, while abundant, are dispersed and disjointed across the Earth’s surface.

Drawing a parallel, consider how mountainous regions harbor isolated valleys where people speak distinct dialects shaped by their seclusion. Nature mirrors this: Species in isolated climatic niches evolve distinctly, creating a diverse and unique tableau of life.

The specter of climate change, however, casts a long shadow over these insights. A world undergoing rapid warming might witness once vast climates fragmenting further. Such shifts could challenge species, compelling them to traverse daunting landscapes to find suitable habitats. If these once expansive climates recede, it could disrupt the entire balance of species interactions.

Understanding the interplay between biodiversity and climate is not merely an intellectual pursuit. It provides direction in helping people protect and appreciate the diverse symphony of life in our evolving world.

Catherine Graham receives funding from Swiss National Fund, European Research Council.

Dave Roberts received a stipend from WSL when he was a Fellow there during his stay in Switzerland when this work was initiated.

Marco Túlio Pacheco Coelho does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.