The Galapagos Islands are home to some of the world’s most unique wildlife, including the marine iguana – the only seagoing lizard on Earth. But climate change and human activity threaten to make this iconic lizard endangered.
If you’re short on time, here’s a quick answer to your question: The marine iguana is at risk of endangerment due to rising ocean temperatures, plastic pollution, oil spills, and invasive species in the Galapagos Islands where it lives.
In this article, we’ll explore in detail the reasons this reptile may soon be classified as endangered by the International Union for Conservation of Nature (IUCN). We’ll look at how climate change impacts the marine iguana’s algae diet, why plastic waste harms its environment, how the tourism industry and human population growth increase disturbance, and the dangers invasive species pose to the lizards.
Rising Ocean Temperatures Impact Marine Iguana Diet
El Niño Causes Algal Shortages
The main staple in the marine iguana diet consists of nutrient-rich green and red algae. However, during El Niño events, which are characterized by unusually warm ocean temperatures, algal blooms dramatically decline.
With the sea surface temperature increased by 3-4°C, the algae the iguanas rely on struggle to survive.
Warmer Temperatures Kill Algae
The higher ocean temperatures brought by El Niño essentially boil the algae, preventing further growth and leading to mass die-offs. One study conducted over a strong 1997-98 El Niño event found that algal production decreased by up to 97% in certain areas.[1] With their main food source decimated, marine iguanas struggle to find enough to eat.
Lack of Food Causes Starvation
Marine iguanas have adapted the ability to shrink their body size during El Niño-induced famines to require less food. However, many still starve to death when the algal crashes drag on for months. During the particularly strong 1982-83 and 1997-98 El Niño events, marine iguana mortality reached between 60-90% on some islands.
If El Niño events increase in frequency and severity due to climate change, as many models predict, it could spell trouble for marine iguana populations already classified as endangered. Their specialized algae diet and island habitats leave them vulnerable to shifts in ocean temperatures.
Protecting algal beds and reducing further ocean warming may prove key to ensuring the marine iguana persists despite the changing climate.
Plastic Pollution Poses Dangers
Plastics Disrupt Marine Ecosystems
Plastic pollution has become ubiquitous in the oceans, with an estimated 8 million metric tons entering the marine environment each year. Plastics take hundreds of years to degrade, breaking down into tiny microplastics over time.
These microplastics make their way into the food chain, causing disruption at every level of the marine ecosystem.
Sea turtles and marine iguanas often mistake plastic for food. A 2015 study found that over half of the juvenile sea turtles surveyed had plastic in their stomachs. The plastic can cause internal lacerations and blockages in the digestive tract, leading to malnutrition, intestinal damage, and potentially death.
Toxins From Plastics Accumulate in Food Chain
As marine organisms ingest microplastics, the toxins leach from the plastics and bioaccumulate up the food chain. This means that top predators like marine iguanas end up with extremely high concentrations of toxins in their bodies.
Studies have detected concerning levels of phthalates and BPA in marine iguanas in the Galapagos Islands. These endocrine disrupting chemicals can impair reproduction, thyroid function, and neurological development. They have also been linked to cancer and obesity.
Marine Iguanas Eat Plastic They Mistake for Food
Marine iguanas feed almost exclusively on nutrient-rich algae. However, pieces of plastic can appear similar to algae, causing the iguanas to accidentally ingest it.
A 2018 study found that marine iguanas had the highest incidence of plastic ingestion out of three Galapagos reptile species. The plastic items included fragments, threads, foams, and films.
Ingested plastic that traps residual food can give marine iguanas a false sense of satiation. This leads them to eat less nutritious algae, resulting in malnutrition. Plastics can also cause life-threatening intestinal blockages.
Oil Spills Degrade Marine Iguana Habitat
Fuel Tanker Accidents Cause Oil Spills
The Galapagos Islands, located about 620 miles off the coast of Ecuador, are home to an incredible diversity of wildlife found nowhere else on Earth. This includes the unique marine iguana, the only sea-going lizard.
Unfortunately, these remarkable animals are being threatened by an increasing number of oil spills from fuel tankers passing through their habitat.
Over 150 fuel tankers go through the Galapagos Marine Reserve every year, carrying oil from ports on the mainland to other parts of the world. With the narrow passages and strong currents surrounding the islands, accidents are common.
When tankers strike the rocks or reefs, this often leads to shipwrecks and massive oil spills.
For example, in 2001 the tanker Jessica ran aground near San Cristobal Island, dumping 240,000 gallons of fuel into the reserve. Even larger was the spill from the OCP tanker in 2018, which released nearly 1 million gallons of oil into the pristine waters.
Oil Coats Shorelines and Reefs
When these devastating spills occur, the thick, heavy crude oil doesn’t quickly dissipate. Ocean currents end up pushing much of it onto the islands’ shorelines. This coats the beaches and shallow reefs in a black, tar-like goop.
Iguanas rely on clean rocks and reefs near the water’s edge for basking, regulating their body temperature. But the oil residue sticks to their skin, compromising their ability to thermoregulate. Even worse, they end up ingesting the toxic oil when grooming themselves, leading to serious digestive issues.
The oil also smothers intertidal algae, reducing the food supply for marine iguanas. And it poisons the reef ecosystems around the islands that provide habitats for diverse wildlife.
Pollution Limits Safe Access to Food and Nesting Sites
By contaminating essential iguana feeding and congregation sites, the oil spills force the marine lizards to search farther afield for clean areas. But this leads them into unsafe territories, including busy shipping lanes, where they risk getting struck by passing vessels.
Oil slicks washing up on nesting beaches are also a major threat. Female iguanas have a difficult enough time finding suitable areas to lay their eggs in the Galapagos’ harsh, lava-strewn terrain. Now they have to pick their way across oily sands to reach safe nesting sites, if these even exist post-spill.
One study of a beach on San Cristobal Island found only 12%% of it remained suitable for nesting after an oil spill.
Unless fuel transportation through the Galapagos can be better regulated, oil spills will continue threatening marine iguanas. More protected marine zones and enforced lower speed limits for tankers could help give these unique lizards a fighting chance.
Invasive Species Compete for Resources
The Galapagos Islands are home to many unique species, including the iconic marine iguana. However, in recent decades, the introduction of non-native species has threatened the survival of the marine iguana.
Let’s examine how invasive species are competing with the marine iguana for limited resources.
Introduction of Non-Native Species
The Galapagos Islands are located over 600 miles off the coast of Ecuador and were historically isolated. This allowed unique species like the marine iguana to evolve in the absence of predators. However, human activity has led to the introduction of many non-native species that now threaten endemic wildlife.
Some problematic invasive species include feral cats, black rats, dogs, pigs, and goats. These animals were likely introduced accidentally via ships or intentionally to serve as livestock. Without natural predators, their populations have exploded, decimating native species.
Competition for Food and Nesting Territories
The marine iguana predominantly eats green and red algae located in the intertidal zone. However, grazing animals like goats also consume algae, resulting in food shortages. One study found that iguanas on islands with goats were smaller and had higher mortality compared to goat-free islands.
Invasive species also restrict access to nesting areas. The removal of vegetation by grazing animals exposes nests to harsh weather and predators. Feral cats and rats directly raid exposed nests and feed on eggs and hatchlings.
Predation of Eggs and Hatchlings
As mentioned, feral cats and black rats pose a substantial predatory threat. One analysis found that feral cats alone kill between 1,000 to 10,000 marine iguanas each year, mostly juveniles.[1] Rats also feed on juvenile iguanas and pilfer eggs from unattended nests.
Beyond direct predation, these invasive mammals transmit diseases and parasites. For example, cats have spread toxoplasmosis, which has led to marine iguana die-offs in the past.[2]
Tourism and Development Increase Disturbance
Visitor Activity Disrupts Nesting
The Galapagos Islands are a popular tourist destination, receiving over 275,000 visitors per year. Unfortunately, increased human presence has disrupted the marine iguana’s nesting habits. Tourists often approach nesting areas too closely, frightening female iguanas and causing them to abandon their nests.
Even well-meaning tourists who want to observe the nesting process can inadvertently scare iguanas. Conservation efforts aim to protect key nesting sites by restricting access during breeding season.
Construction Impacts Habitats
To accommodate growing tourism, new hotels, restaurants, and other facilities are built each year in the Galapagos. Construction often occurs right along the coast, eliminating prime marine iguana habitat. Road development also fragments areas used by iguanas for basking.
Scientists estimate over half of the original nesting beaches have already been lost. Further coastal development could destroy the few remaining undisturbed areas. Eco-friendly construction standards have been proposed to minimize habitat impact.
Growing Human Population Strains Resources
The islands’ permanent human population grows 2-3% annually. More residents require increased infrastructure, placing pressure on the fragile island ecosystem. Freshwater is extremely limited, and increased demand threatens the survival of all species.
Expanding agricultural operations also reduce vegetation that stabilizes the sandy nesting beaches used by marine iguanas. Additionally, native species must now compete with feral dogs, cats, rats, and other invasive animals introduced by humans.
Managing the islands’ booming human population is crucial for protecting all native wildlife.
Conclusion
The marine iguana is a vital part of the fragile Galapagos ecosystem. But rising ocean temperatures, plastic pollution, oil spills, invasive species, and increasing human activity threaten these animals and their habitat.
Conservation efforts are needed to curb climate change, protect marine environments, control invasive species, and manage tourism impacts. If these issues can be effectively addressed, the unique marine iguana may be able to avoid endangerment and continue thriving in its island home.
