Under the microscope: Studying the effects of climate change in Costa Rica
Dr Robert Puschendorf, Lecturer in Conservation Biology, charts the opportunities and challenges facing this tropical paradise
Staring out from its cover is a harlequin toad. “I used to play with these when I was a child,” Rob says. “The rivers and streams close to where we lived were full of them. Then one day they vanished. It was like my toys had been taken away. I wanted to know why.”
The childhood Rob refers to was spent in Costa Rica. Home to five million people, it covers a land area of just 51,000km2. On one side is the mighty Pacific Ocean, on the other the stunning waters of the Caribbean Sea. Rainforests rub shoulders with 4,000m high mountains. The combination creates a paradise, an idyllic place to grow up. But Costa Rica is about more than golden beaches and warm climes.
For while it may be small in size, the country is a big player globally when it comes to its rich biodiversity. In fact, the indication is that it has the same degree of diversity as the United States and Canada combined.
That is not solely down to its geographical location. This is a nation in touch with its natural side. In 1970, three scientists established the country’s National Park system. Initially protecting 11 areas around the country, it meant the flora and fauna within those sites were preserved. Other Latin American rainforests – most notably the Amazon in Brazil – have continued to be decimated by deforestation. But Costa Rica’s have recovered. People have found ways to make money from the forest in ways other than cutting it down.
That ethos extends to its infrastructure. Hydropower and geothermal are the main energy sources. And if roads need to be built, the engineers work with conservationists to ensure the nature is preserved. It has led to Costa Rica becoming known as the 'Switzerland of the Americas'. “Paradise is the right word to use,” Rob says. “Growing up, there was zero crime, the weather was good. And in 20 minutes, you can drive from city to dry forest, plant forest and rainforest.”
That kind of diversity is another part of what makes this such a special place to study climate change. And Rob and those he works with are following a well-trodden path.
Conservation research has been taking place within Costa Rica’s borders for decades, if not longer. That has created an unsurpassed level of knowledge of what exists. It also serves as a benchmark when scientists are looking for signs of change. And that change is becoming ever more apparent.
“The first thing you feel is the heat,” Rob says. “After an 11-hour flight from the UK, it’s always a shock to the system. And when we go in April, it’s the hottest time of the year in Costa Rica.”
Rob has been taking conservation biology students from Plymouth to Costa Rica for almost a decade.
But before they even reach the tarmac of Juan Santamaría International Airport, the uniqueness of the landscape is already apparent. The capital city of San Jose sprawls across the valley. Forests are evident out of every window. Behind them are towering mountains, and volcanoes that cast menacing shadows. The airport has gift shops full of tropical trinkets. And the flourishing palm trees outside its automatic doors are a small clue of what is to come.
Within 20 minutes of clearing customs, civilisation is already a distant feature in the rear-view mirror. A minibus journey winds through mountain passes and national parks. But after three hours, it arrives at the La Selva Biological Station. Surrounded by forest, and located right by a river, this will be the students’ base for the next 10 days. The wildlife is quite literally within touching distance. But while it is stunning, light clothes, liquid, and lots of showers are the order of the day.
“The physical environment is a challenge,” says Rob. “You’re talking 100% humidity, and the build-up to monsoon time. Only the library has air-conditioning. I have heard of students sleeping in there to stay cool.”
Once they acclimatise, La Selva offers a diversity most of the students will never have seen. More than 2,000 species of plants. 125 mammals. 470 birds. 87 reptiles. Tens of thousands of insect and other arthropod species. That can mean tens of thousands of bites. But in essence, this is an incredibly safe environment from which to launch students into the remarkable, but challenging tropical forest. The field station also has an unrivalled resource base – expert guides, a herbarium, lab and classroom facilities.
Listening to Rob talk about the species in La Selva is like listening to someone read an encyclopaedia aloud. In and around the research station there are jaguars, pumas, four species of monkeys, and sloths. During dinner, you may be lucky enough to see a flock of critically endangered green macaws fly over. There are crested eagles as well. Where the students sleep there are bats roosting on the roof and you can walk right up to them. In one of the national parks, there are more than 14,000 different species of moth. Compare that to the UK, where there are 2,500 in total. Closer to the ground, poison dart frogs are everywhere. The males engage in territorial combat. The females lay their eggs on leaves, put their tadpoles on their backs and take them into the trees where they feed them on other fertilised eggs. There are turtles in the rivers, too. And all sorts of fish.
“We do stuff they’ve never done before like night walks. Going into the forest at night is a completely different experience,” Rob says. “Hopefully they will be excited, because enjoying it is crucial. For some, it is such an assault on the senses.”
“I guess what I first loved about frogs is that they’re not going to kill me.”
As reasons to focus on a particular creature go, it’s not an unreasonable one. Especially when you realise that much of the wildlife in Costa Rica isn’t quite so considerate. “Then I realised they have really interesting behaviours and biology,” Rob adds. “I got hooked as a child.” It is four decades since Rob’s childhood encounters with the frogs of Costa Rica. But his passion for understanding them, and the threats facing them, is as strong as ever.
In 2015, he and colleagues in Costa Rica discovered the first new species of glass frog in the country since 1973. Hyalinobatrachium dianae, also known as Diane’s bare-hearted glass frog, bears a striking resemblance to arguably the world’s best known puppet amphibian. It took two years of field and lab studies to verify. “It was the kind of find we hope will inspire future generations of biologists,” Rob says. “We want them to keep searching, being curious and exploring. Understanding the biology of a species fundamentally requires hard work in the field. But the passion to discover is what makes biology such an exciting career.”
His current work focuses on another critically endangered species, Craugastor ranoides. Found in the Guanacaste Conservation Area, close to the border with Nicaragua, disease and climate change have seen it disappear from its original habitats. It now persists only in locations where the pathogen cannot thrive. But this isn’t sustainable. In 2014/15, a strong El Niño caused rivers to dry out. A freak hurricane also caused landslides that buried streams under rubble. These natural hazards are now an ongoing threat that, unlike the water the frog needs for survival, has not evaporated. The only solution will be to try and move a whole population.
But that is not something that can be done on a whim. Before any human intervention can be advocated, human evidence is needed. To gather that, Rob is working with Plymouth colleagues Dr Katherine Herborn and Dr Alex Wilson , and partners from the UK and Costa Rica. The aim is to conduct science that will deliver lasting benefits. And one good thing about a country with such a rich conservation heritage is that it is often very receptive to new ideas.
Searching for a tiny frog in a rainforest sounds considerably more different than the proverbial hunt for needles in haystacks. But technology is on the scientists’ side.
As a thermal biologist, Katherine takes the lead on the night-time searches. A combination of thermal cameras and drones can pinpoint a single frog in a vast area. Alex, a behavioural ecologist, then observes it in its natural environment. And once it is captured, the team works to establish the frog’s gender and swabs it to check for the presence of disease. The frog is then marked so it can be recognised again, and chipped so its movement can be tracked. Another colleague, Dr Xavier Harrison, looks at their skin microbiome to help define what a healthy population should look like. It also gives an insight into how able they are to defend themselves from emerging infectious diseases.
“All of this data is crucial,” Rob says. “If we want these frogs to survive we need to know the conditions they operate in. It is only then that we can work with our partners and come up with a long-term plan.”
Costa Rica’s diversity is not all on land.
Its Pacific coast is home to coral reefs. But these are also under threat from climate change. In 2009, an extreme weather event resulted in rapid sea temperature drops of up to 10 degrees. Combined with widespread rise in harmful algal blooms, it caused a collapse of the reefs in the Eastern Tropical Pacific. Coral cover at some sites decreased by between 20% and 100%. And while some sites have seen a recovery, others most definitely have not. “The demise of coral reefs is normally linked to global warming and marine heatwaves,” Rob says. “That wasn’t the case here and it’s something we need to consider. It emphasised the importance of tailor-made conservation strategies.”
Costa Rica has a history of making such decisions. And the positive decisions made more than 50 years ago continue to yield positive impacts today.
From 11 protected areas in 1970, there are now 186. That covers 31 National Parks, 34 wildlife refuges, 15 biological and forest reserves, 11 wetlands, and 33 protected zones. Costa Rica also protects more than 15% of its marine territory in ten Protected Marine Parks and other Marine Protected Areas.
This environmental commitment has in no small part been aided by the country’s relatively stable political situation. In 1989, that was threatened when it found itself at the centre of a Cold War scandal involving the notorious American General, Oliver North. It is more than faintly ironic that the airstrip at the centre of the controversy is now one of Rob’s field sites, in the Guanacaste Conservation Area.
When it comes to the biggest threats facing the country’s wildlife, Rob is clear. Disease, yes. Climate change, absolutely. But there is also a third aspect – complacency.
Costa Rica has thrived because it has been closely managed. The people feel a sense of pride, a genuine connection to the landscape. “The problem is they don’t realise how lucky they actually are,” says Rob. “And I was probably the same when I lived in Costa Rica. If we are to keep protecting our environment that needs to change.”