Parts of Delhi, Mumbai, Chennai, Kolkata and Bengaluru, India’s largest cities, are slowly sinking, mainly due to overextraction of groundwater, according to a recent study, reports Mongabay India’s Manish Chandra Mishra.

Researchers used eight years of satellite radar data and found that 878 square kilometers (339 square miles) of land across the five megacities show signs of subsidence. This leaves more than 2,400 buildings at high risk of structural damage. If current trends continue, the number could rise to more than 23,000 buildings in the next 50 years, the study found.

“Our motivation to study land subsidence and building damage risk in Indian megacities stems from the absence of prior research that explicitly investigates land subsidence and links differential settlement with observed structural damage,” Nitheshnirmal Sadhasivam, study co-author from Virginia Tech, U.S., told Mongabay India. “While the impact of land subsidence on infrastructure is a well-recognised geohazard globally, in cities such as Jakarta, Mexico City and Tehran, its implications for building stability in India have not been systematically assessed.”

The study found that roughly 1.9 million people across the five cities live in areas that are sinking at a rate of more than 4 millimeters (0.16 inches) per year.

Delhi, Chennai and Mumbai face the highest levels of subsidence: the annual rates of subsidence reach 51 mm (2 in) for parts of Delhi, 31.7 mm (1.25 in) for Chennai, and 26.1 mm (1 in) for Mumbai.

“Across all five megacities, groundwater dependence and overexploitation emerge as the dominant local drivers of subsidence,” Sadhasivam said. “As groundwater is withdrawn, the resulting loss of pore pressure in compressible aquifer layers causes gradual compaction, leading to measurable land surface sinking over time.”

Vikas Kanojia, an urban designer not involved in the study, told Mongabay India that Delhi’s rapid growth has outpaced groundwater recharge. “Many zones in NCR [National Capital Region] are facing water shortage due to deficient ground water recharge versus demand,” he said. “The ground water table has drastically dropped in many areas of NCR leading to change in the density of the sub-soil structure.”

However, some areas show signs of recovery, Mishra writes. Parts of Dwarka in southwest Delhi, for example, are rising, thanks to groundwater recharge programs like rainwater harvesting and restrictions on extraction.

“Regions like Dwarka in Delhi demonstrate that policies promoting groundwater regulation and artificial recharge can help stabilise the ground and partially reverse subsidence trends,” Sadhasivam said. “However, recovery is not always uniform. When some areas experience uplift while adjacent zones continue to subside, sharp gradients in ground motion result, creating transitional stress zones.”

Researchers say the cities’ land subsidence can amplify impacts of flooding, earthquakes and other disasters on the already overburdened infrastructure.

Read the full story by Manish Chandra Mishra on Mongabay India here.

Banner image: Land subsidence is putting buildings in five Indian megacities, including Delhi, pictured here, at high risk of structural damage. Image by Pinakpani via Wikimedia Commons (CC BY-SA 4.0).

Founder’s Briefs: An occasional series where Mongabay founder Rhett Ayers Butler shares analysis, perspectives and story summaries.

Off the western coast of Sumatra, Indonesia, the Mentawai Islands rise from the Indian Ocean in a patchwork of forests and rivers where macaques, gibbons and hornbills thrive. Among the Indigenous Mentawai, an ancient cosmology called Arat Sabulungan continues to shape how people understand the natural world. It teaches that every tree, river and animal is inhabited by spirits whose balance must be respected. Though Islam and Christianity have spread through the islands, many young Mentawai still join their elders in ritual offerings before cutting trees or casting nets, reports Keith Anthony Fabro for Mongabay.

“Mentawai youth today reinterpret their ancestral heritage in diverse ways,” researcher Dwi Wahyuni from Imam Bonjol State Islamic University, told Fabro.

A recent study by Dwi and colleagues explored how Arat Sabulungan interacts with modern religion and conservation. Conducted in five villages on Siberut and Sipora islands, it found that youth raised in churches or mosques often still honor ancestral rituals. One example is buluat, a ceremony performed before felling trees, which includes an offering to the tree’s spirit and a promise to replant fruit trees. “Any trees we clear are replaced … If we do not replant, the land will not thrive,” an elder said. The researchers observed that such traditions act as informal safeguards against overexploitation.

Yet Arat Sabulungan faces mounting pressure. Logging, which resumed after a moratorium ended in 2001, has stripped much of Siberut’s forest. “Forest exploitation by large companies and local actors has caused massive deforestation,” the study warned. The loss of forest, it said, undermines not only ecosystems but also the rituals and knowledge that depend on them.

Some scholars question the study’s optimism. Darmanto Darmanto of the Czech Academy of Sciences’ Oriental Institute argued that Arat Sabulungan does not automatically prevent forest exploitation and that brief fieldwork cannot capture its complexity. He warned against romanticizing Indigenous spirituality “as the good kind of primitive spiritualist that an urban audience wants to hear about.”

Dwi acknowledged these critiques, noting that his research aimed to show how cosmology interacts with economic and political forces.

“Rather than depicting them as purely green traditions, I suggest they form a cultural framework for negotiating human-nature relations,” he said. For the Mentawai, the fate of those traditions may depend on the fate of the forest itself.

Read the full story by Keith Anthony Fabro here.

Banner image: A sikerei, or shaman, walks in the forest. Image by The etnic via Wikimedia Commons (CC BY-SA 4.0).

The European Union has voted to postpone implementing a key antideforestation law for the second year in a row, citing technical concerns. Critics of the move warn that a delay and other proposed changes will further weaken the law.

On Nov. 26, the European Parliament voted 402 to 250 in favor of an amendment that delays a start date for the landmark European Union Deforestation Regulation (EUDR) and introduces an array of exemptions to the law.  When the law goes into effect, it will ban EU nations from importing goods like soy, beef, cocoa and palm oil that come from areas deforested after 2020.

If the amendment is ratified, it will delay EUDR implementation another year to Dec. 30, 2026, with an additional grace period for small businesses through June 30, 2027. The EUDR was originally set to take effect at the end of 2024, before being pushed forward a year to December 2025.

“EU lawmakers are subjecting the EUDR to death by a thousand cuts,” Nicole Polsterer, a campaigner at Netherlands-based nonprofit Fern, told Mongabay by email. “The endless carousel of attempts to revise and even destroy a law that was passed with a large democratic mandate two years ago, are a farce.”

Along with the delay, European lawmakers also made a series of changes to the original law.

Printed books and newspapers were removed from the scope of the law, a move perceived to benefit the forestry industry.

Small operators that produce their own goods and are from countries classified as “low risk” under the EUDR, which includes EU nations, the U.S., China, Australia and Canada, will be largely exempt.

Dozens of businesses and NGOs, including food conglomerate Nestlé, published a joint letter on Nov. 17 saying a further delay creates market uncertainty and instability. Conservation NGO WWF called the move “a chaotic and unmanageable situation.”

The European Parliament also proposed a review window for the law, which would allow politicians to make further changes over the coming months.

“Worryingly, parliament has asked the EU Commission to undertake a ‘simplification review’ of the law and come back with a report by April 2026,” Fyfe Strachan, policy and communications lead at Earthsight, an NGO, wrote in a statement. “This report could trigger another round of amendments, compounding the legal uncertainty created by today’s vote.”

According to Polsterer, companies that had prepared for the law’s implementation in just over 30 days will now face extra costs to adapt to additional changes.

The European Parliament’s proposed delays and revisions to the EUDR will now go into informal negotiations between the EU’s three branches of government. A final text will then be returned to the parliament for ratification.

Banner image: European Parliament during voting session on Nov. 26. Image courtesy of the European Union.

As winter closes in across much of North America, migratory birds are heading south to warmer climes and more abundant food. But until recently, scientists didn’t have a good understanding of exactly where they went.

Researchers from the Wildlife Conservation Society (WCS) and the Cornell Lab of Ornithology U.S. analyzed observations from eBird, a global citizen-science database of sightings submitted by bird-watchers. They found that in 2022 more than half of the 314 migratory bird species they studied went to the five great forests of Central America.

They write that 5 billion migratory birds funnel through Central America each year. Many stop in the rainforests, alpine wetlands and mangroves of the five great forests: Selva Maya in Mexico, Belize and Guatemala; Moskitia in Honduras and Nicaragua; Indio Maíz-Tortuguero in Nicaragua and Costa Rica; La Amistad in Costa Rica and Panama; and the Darién in Panama and northern Colombia. Collectively, these forests cover more than 10 million hectares (2.5 million acres), the researchers write.

The five great forests. Image courtesy of Trillion Trees.

The study found that many species spend the entire winter in these forests, including one in four wood thrushes (Hylocichla mustelina). Others, including one-third of broad-winged hawks (Buteo platypterus) and 40% of cerulean warblers (Setophaga cerulea) use the forests as a stopover for journeys farther south. Cerulean warbler populations have declined by roughly 70% since the 1970s.

“The density of migratory warblers, flycatchers, and vireos crowded into these five forests is astounding, and means that each hectare protected there safeguards a disproportionate number of birds,” study co-author Viviana Ruiz Gutierrez, director of conservation science at the Cornell Lab of Ornithology, said in a statement.

The five great forests, crucial for both migrating birds and permanent residents like jaguars, tapirs and monkeys, are increasingly under pressure from illegal deforestation, lead author Anna Lello-Smith, a conservation scientist at WCS, told Mongabay in a video call.

The two northernmost forests, Selva Maya and Moskitia, have lost roughly a quarter of their area in the last 15 years. “They were the most important for migratory birds in terms of the percent of populations that they’re supporting, but those are also some of the most threatened by illegal cattle ranching and fire,” Lello-Smith said.

While the migratory birds are concentrated in the five forests over winter, the study found that during the breeding season, they spread across the eastern U.S. and Canada. There, they face threats from additional habitat loss and degradation, house cats, vehicle collisions and pollution.

Lello-Smith said she hopes this research will foster more stewardship connections between the Central America and North America.

“These birds are really connecting people and communities between these distant landscapes, and we all have this shared responsibility to protect their habitats throughout their range and to work together to figure out solutions,” she said.

Banner image: A cerulean warbler. Image by DiaGraphic via Wikimedia Commons (CC BY 2.0).

Reptile species found only on islands are significantly more vulnerable to extinction than their mainland counterparts, yet remain vastly overlooked by researchers, according to a recent study.

“Reptiles, partly due to their ability to endure long periods without food or water, are particularly effective island colonizers,” Ricardo Rocha, study co-author and an associate professor at the University of Oxford, U.K., told Mongabay by email. “Across the globe, they have co-evolved with a wide range of island taxa and play a crucial role in maintaining island ecosystem dynamics. Yet, despite this importance, they are often overlooked in favour of more groups perceived as more charismatic such as birds or mammals.”

The researchers reviewed published scientific research on nearly 12,000 known species of reptiles recognized as of May 2021, and found that 2,543 species, or 21%, are confined to islands.

About 30% of these island-restricted species are currently threatened with extinction, the study found, compared to 12% of mainland reptile species.

Yet despite their much higher extinction risk, island species were the focus of just 6.7% of the published research from 1960-2021. The review also found that nearly half of the island-restricted species, have no published research targeting them at all.

“The current research levels are insufficient to meet the needs of defining informed conservation strategies for a large number of threatened species,” Sara Nunes, study lead author from the University of Porto, Portugal, told Mongabay by email.

What research does exist on island-restricted reptiles tends to focus on large, more widespread species, while smaller, more recently described and high-altitude species remain largely unstudied, the review found.

“This can lead to species being overlooked, especially species in locations more difficult to access, smaller animals that can be more difficult to sample, and therefore less studied,” Rocha said.

Certain “unusual or striking traits” grab more research attention, he added. For example, venomous reptiles are more frequently studied because they’re relevant to human health, Rocha said. The Okinawa habu (Protobothrops flavoviridis), a species of pit viper found only in the Ryukyu Islands of Japan, was the most studied island-restricted reptile, the review found.

Similarly, evolutionarily unique species attract more research. For instance, the tuatara (Sphenodon punctatus), which diverged from lizards and snakes about 250 million years ago and is only found in New Zealand, was the second most studied island-restricted reptile, the review found.

“The risk is that species perceived as less appealing are less likely to be studied and this might have severe conservation implications,” Rocha said.

He added in a statement that focusing scientific and conservation efforts on islands and their unique reptile species “is essential to prevent irreversible losses.”

“Imagine visiting Komodo Island and not seeing its dragons,” he said. “It just wouldn’t be the same, would it?”

Banner image: O’Shaughnessy’s chameleon (Calumma oshaughnessyi), restricted to Madagascar. Image courtesy of Ricardo Rocha.

A recent study from the U.S. state of California finds that the public reported more encounters with wildlife in times of drought. Researchers say they expect such drought-driven human-wildlife interactions in other areas also facing water shortages — a growing problem amid climate change.

The researchers analyzed more than 31,000 wildlife-related incidents reported by members of the public to the California Department of Fish and Wildlife (CDFW) between 2017 and 2023. The reports fell into four categories: property damage; general nuisance including negative interactions unrelated to property damage; instances when people believe an animal could potentially cause conflict; and simple sightings.

Most reported incidents, more than 18,000, involved property damage. These ranged from attacks on livestock by pumas and coyotes, to landscaping damage by wild pigs and turkeys, to home damage by black bears.

Researchers focused on the roughly 23,000 incidents of direct conflict involving property damage and general nuisance. They found that American black bears (Ursus americanus) were the most reported species, followed by wild pigs (Sus scrofa), pumas (Puma concolor), coyotes (Canis latrans), North American beavers (Castor canadensis), bobcats (Lynx rufus), wild turkeys (Meleagris gallopavo), mule deer (Odocoileus hemionus), raccoons (Procyon lotor) and gray squirrels (Sciurus griseus).

The study found a strong link between incident numbers and precipitation data: wildlife conflicts increased significantly as precipitation dropped.

The total number of reported incidents increased 2.11% for every 25-millimeter (1-inch) decrease in precipitation. Moreover, areas with higher tree and population density were associated with increased reports of conflict, the study found.

Lead author Kendall Calhoun, a postdoctoral researcher at the University of California, said drought-induced resource scarcity drives much of the conflict. Carnivores target livestock, for example, when their natural prey is limited. Other species may turn to crops, gardens or homes.

“During resource scarcity, other animals, like deer, elk, and wild turkey, may be more inclined to take crops or other plants from people’s properties as well. Black bears are known to come near people’s houses to look for food, often causing property damage in the process,” Calhoun told Mongabay by email.

Researchers say they expect drought-driven conflict with wildlife will extend far beyond California.

“We expect this effect will be particularly strong in areas that are prone to drought and have strong seasonal swings in water availability like California and other Mediterranean-climate ecosystems with cool, wet winters and hot, dry summers,” Calhoun said.

Climate scientists project that both California and Europe’s Mediterranean will become drier and prone to drought amid climate change. Both regions are densely populated, setting the stage for increased conflict between people and wildlife, especially during hot, dry summer months, Calhoun said.

He added there’s a need to meaningfully address climate change to get to the root of the problem. “Building climate-resilient landscapes should be a very clear goal for future land and wildlife management,” Calhoun said.

Banner image: An American black bear standing on a fence in Canada. Image by Henry C. Wong via Pexels.