It has been 10 years since the world watched in horror as the Indian Ocean earthquake and tsunami of 2004 left coastal communities across Southeast Asia and beyond in shambles. Waves the size of five- to 10-story buildings drowned the coastlines of Sumatra, Thailand and the Andaman Islands, toppling homes and hotels like dominoes and killing an estimated 230,000 people. Entire ecosystems were ruined as the ocean inundated coastal wetlands, ripped mangrove forests from their roots, left sea life high and dry and raked debris over delicate coral reefs. For many communities whose beautiful shores and abundant wildlife were the foundation of a thriving tourism industry, it was ecological bankruptcy.

A decade later, natural forces and human intervention have largely nursed the affected environmental areas back to health. “Although some coastlines, beaches, beach dunes, river courses were significantly altered [by the tsunami ...] these ecosystems are functional and intact,” said Stuart Campbell, director of marine programs with the Wildlife Conservation Society’s Indonesia chapter.

In the years since the tsunami, tropical rains flushed saltwater out of estuaries and rivers and back into the ocean. Beaches were restored naturally as ocean waves deposited new sand onto shores. Mangrove trees have been replanted. Coral reefs that were damaged have started to regrow, and sea life has returned to the bays. Soils that were poisoned by heavy metals were far less toxic a few years later. 

“One month after the tsunami, we expected to find just a few species” off the shore of Aceh in Indonesia, “but it appeared to be a rich ecosystem with very high abundance” of sea life, said Witold Szczucinski of Adam Mickiewicz University’s Institute of Geology in Poland. The ecological changes “were really remarkable, but over the course of the next few years, the coastlines were mainly rebuilt,” in some cases in just a few months, Szczucinski said.

Instead, ecologists say the biggest threat to the region’s ecosystems is not nature, but man. Overfishing, deforestation, coastal mining, the rise of tourism and other human activities continue to concern environmentalists, who say the region’s natural resources are already badly stressed. In fact, many of the problems associated with the tsunami were there before the waves hit and were the result of the region's burgeoning tourism industries. Large, waterfront resorts resulted in altered landscapes, with mangrove forests or seagrass meadows removed to make beaches more desirable to sunbathers, the World Wildlife Fund reported. Sometimes, seaside resorts dump their sewage directly into the ocean. A single golf course in Thailand needs on average as much water yearly as do 60,000 rural villagers, according to the Global Development Research Center.

“I’m always sort of frighteningly shocked when I go out diving and I see dive masters and their clients standing on the coral [in Thailand],” said Catherine Plume, managing director of the coral triangle program at WWF. “Do you realize you’re destroying your own livelihood by standing on this?”

It was the day after Christmas 2004 when the massive underwater earthquake struck off the coast of Sumatra, Indonesia. It measured a magnitude of 9.1 on the Richter scale, the third-largest earthquake ever recorded on a seismograph. The shaking lasted eight to 10 minutes. Shock waves were felt as far away as Alaska.

The immediate impacts of the resulting tsunami on the environment were many and disastrous. The biggest hazard, according to the Global Development Research Center, was the amount of debris and waste that got flushed into the surrounding bays. The sheer volume of stuff, including hazardous materials like asbestos, oil fuel and other chemicals, strained the communities that had to clean it up.  

Indonesia suffered the brunt of the disaster. In Aceh, on the island of Sumatra, ecologists found evidence of damage to 30 percent of coral reefs and 20 percent of seagrass beds. More than half of Aceh’s west coast beaches were degraded. In Sri Lanka, saltwater, sewage and wastewater contaminated an estimated 62,000 groundwater wells, affecting supplies of drinking water.

The impact of the tsunami in Thailand was seen mostly along the country’s western Andaman coast, whose shoreline was dotted by resorts. Ecologists estimated that between 15 percent and 20 percent of the region’s coral reefs sustained damage. Some coral reefs were affected by the tsunami, mainly as the result of backwash. Coral can take hundreds of years to recover, said Szczucinski. “But you must keep in mind that it was less than 20 percent of the coral reefs that were hardly damaged,” he said.

Environmental concerns were compounded following the tsunami, especially in places like Thailand, where the tourism industry has boomed. The number of resorts in Thailand “increased dramatically” after the disaster when land along the coast became cheap, Szczucinski said. Thailand’s tourism industry has been steadily rising over the past 15 years and hit an all-time peak in 2013 – after briefly stalling in 2005 post-tsunami – in large part because of an influx of tourists from China. The country saw nearly 27 million foreign visitors last year, a 167 percent increase from 2000, according to the Tourism Authority of Thailand. Indonesia welcomed nearly 9 million tourists in 2013, a 8.4 percent increase from the previous year. Since 2004, the tourism sector in Indonesia has been “one of the most important engines of growth and development,” according to a study by the Indonesian State College of Statistics.

The region faces other environmental challenges as well. Illegal logging and oil pumping in Sumatra are huge concerns, according to Fred Stolle, a program manager for World Resource Institute’s forest department. Looking at satellite images, he said, it’s easy to see the vast swaths of forest on the island’s interior that have been lost to logging. Thirty years ago, Sumatra was home to huge tiger, elephant, orangutan and exotic bird populations, but widespread development in the pulp and paper industries there has sent their numbers plummeting, according to the International Union for Conservation of Nature.  By some estimates, at the current rate of deforestation, Sumatra could be nearly devoid of forests within 20 years.

In other parts of Southeast Asia, overfishing and illegal fishing continue to deplete fish stocks, said Plume. Unlicensed fishing boats that exceed their catch limits populate the waters around the islands. Local fishermen often remove too many juvenile fish from the breeding population, meaning there are fewer fish reaching breeding age. “In some ways, these large vessels and small vessels are fishing themselves out of business,” she said.

Another major issue across the region is water security. Much of Southeast Asia’s fresh water supplies are polluted or not properly treated, according to the Matador Network. In Indonesia, where the problem of water sanitation is most severe, only 30 percent of city dwellers and 10 percent of villagers have access to clean water.

Drawing firm conclusions about the state of coastal environments in the areas affected by the tsunami before the disaster has proved difficult for ecologists. Many coastal systems in the region were not well studied before the tsunami, Szczucinski said, so scientists have little to compare their recent findings with.

“What did come out of [the disaster] was an awareness about how vulnerable these places are,” Plume said. Had some of the communities affected by the tsunami not cleared their mangroves to allow for construction, for instance, “maybe the flooding wouldn’t have been so bad.”