- Bengaluru’s record-breaking plantation drive has renewed debate over whether mass tree planting is the most effective way to restore urban ecosystems.
- The Miyawaki method can rapidly create dense green cover, but scientific evidence for many of its claimed benefits remains limited.
- Ecologists say greening cities such as Bengaluru requires restoration tailored to their native ecosystems, long-term planning and accountability, not just planting millions of saplings.
Thousands of Bengaluru residents came together late last month in an attempt to set a Guinness World Record for planting the largest number of tree saplings in a single day. Nearly 1.5 million saplings were planted across 240 acres in the drive organised by the Bangalore Development Authority (BDA), with funding from multiple corporate social responsibility (CSR) initiatives and support from environmental organisations.
A growing number of ecologists, however, say the enthusiasm for mass tree planting in cities has outpaced the science behind it.
This tree plantation drive, billed as one of the country’s largest urban greening exercises, was designed using the Japanese Miyawaki method of dense native tree planting, a method that is popular but also has been criticised for overstating its effectiveness.
“The idea is to make Bengaluru greener. There is global warming, so we want to start this movement with the city,” BDA chairman N.A. Haris told Mongabay-India before the event. He said the plantations, spread across lakes, nala buffer zones and public spaces, are intended to reduce the urban heat island effect and build the city’s climate resilience. Authorities say every sapling will be geo-tagged and monitored for survival.
But mass tree plantation is hardly a quick fix to urban green loss.
“What exactly are we trying to achieve? Is it setting a record or greening the city? If it’s ecology, then what environmental problem are we trying to solve?” asks Rajkamal Goswami, a scientist at ATREE who studies forests and biodiversity dynamics.
For Goswami, the Bengaluru plantation drive illustrates how urban restoration is being increasingly approached — heavy on logistics, but light on ecology. “They’re calling these ‘urban forests’, but they are not being planned as part of a long-term urban development plan. We are already destroying existing green spaces as the city expands, while simultaneously trying to green the city without a proper plan.”
As Indian cities lose wetlands, avenue trees and open spaces to rapid urbanisation, planting millions of saplings appears to offer an obvious environmental solution. Previously, Ahmedabad too planted 361,000 plants on July 12 to enter the Guinness World Records.
The scale of such drives also raises questions about costs and accountability. According to media reports, the BDA allocated around ₹880 million for the initiative, although Haris told reporters that the final expenditure would be released only at the end of July. Within days of the plantation, reports of saplings dying had already begun to emerge, reviving concerns over the effectiveness of one-day plantation drives and whether they prioritise measurable ecological outcomes or public optics.
The BDA has promoted the drive as a response to rising temperatures and the urban heat island effect. “We are using the Miyawaki method for tree plantation. The trees will grow fast in three years’ time,” Haris said.
Is Miyawaki the ideal solution?
Over the past decade, the Miyawaki method has become the preferred model for urban greening among governments, corporations and citizen groups alike. Small patches of dense woodland have appeared in Bengaluru, Mumbai, Hyderabad, Chennai and dozens of other cities, promoted as “urban forests” capable of restoring biodiversity, capturing carbon and cooling overheated neighbourhoods.
But ecologists say urban greening is more complex than simply planting more trees. A recent study found that while dense tree canopies generally reduce heat by providing shade in tropical savannah cities such as Bengaluru and Chennai, trees with high photosynthetic activity can release large amounts of moisture through evapotranspiration, increasing humidity and raising the Heat Index, or “feels-like” temperature, in poorly ventilated areas.
The findings suggest that cities need climate-specific planting strategies that consider species selection, canopy structure and landscape design, rather than acting on assumptions that increasing tree cover alone is the solution to warming.
Developed by the late Japanese botanist Akira Miyawaki, the Miyawaki method promises to rapidly restore degraded or urban land by creating dense, self-sustaining “pocket forests” using native tree species. The approach has gained popularity across Indian cities, where it is promoted as a way to restore biodiversity, capture carbon and cool urban neighbourhoods.
But ecologist Pooja Choksi, who specialises in restoration science and monitoring technology, says many of these claims remain inadequately tested. “For most of those claims, the evidence is either weak or non-existent. Many of these claims are made primarily in grey literature and promotional reports rather than in peer-reviewed scientific publications,” she says.
Choksi points to a 2025 systematic review of the Miyawaki method, which found limited scientific evidence supporting many of its widely cited benefits. The review found the strongest evidence for rapid early tree growth and canopy development, although researchers noted that these outcomes may result from intensive soil preparation, irrigation and maintenance rather than the planting method itself.
The review found no empirical evidence to support another widely promoted claim — that Miyawaki forests become self-sustaining after three years. Evidence that these plantations support higher biodiversity or store substantially more carbon than other restoration approaches was also found to be limited, largely because of a lack of rigorous comparative studies.
Researchers note that the method is considerably more resource-intensive than conventional restoration. It relies on dense planting, extensive soil preparation, organic amendments, irrigation, weeding and labour-intensive maintenance during the initial years. Published estimates put the cost of establishing Miyawaki plantations in India at about $32,000 per hectare, although costs vary depending on the site and management practices.
Read more: Can planting trees mitigate climate change? [Explainer]
Ignoring understory and biodiversity
Not all the evidence is critical of the Miyawaki method. A recent study led by socio-ecologist Anirban Roy, which examined the carbon sequestration potential of three Miyawaki forests aged two, four and five years in Bengaluru and Palakkad, found that carbon storage increased as the plantations matured. Five-year-old forests sequestered nearly four times more carbon than two-year-old ones, suggesting the method can contribute to climate mitigation in urban landscapes.
But Roy cautions against equating rapid tree growth with ecological restoration. “One of the biggest drawbacks of the method is its overemphasis on trees. It ignores the importance of herbs and grasses in tropical forest ecosystems,” he says.
According to Roy, the Miyawaki method’s high-density planting approach (around three saplings per square metre), in which species with differing, and at times contrasting, nutrient and water requirements are established simultaneously, may intensify below-ground competition for soil nutrients and moisture, particularly during the early stages of establishment. The dense, uniform canopy also limits sunlight reaching the forest floor, suppressing the growth of herbs, shrubs and other understorey vegetation. “Miyawaki is not fully inappropriate if we can adapt it to the ecological needs of the region by introducing a variety of plants such as herbs and shrubs, apart from just trees,” he says. Staggering planting over time, rather than establishing all trees at once, could also improve structural diversity, he adds.
What remains unknown, however, is how these plantations evolve over decades. Long-term ecological studies tracking Miyawaki forests over 30 to 50 years are virtually non-existent, making it difficult to assess whether they eventually become self-sustaining ecosystems.
That lack of evidence, however, has done little to slow the method’s popularity. “Perhaps people saw it work in Japan, where it was developed under very different ecological conditions,” Choksi says. The rapid early growth of Miyawaki plantations, coupled with the commercial opportunities they create, may also have fuelled their spread. “People see rapid growth during the first few years, mainly due to large inputs of water and natural fertiliser (such as jeevamrut), and assume that after 50 years they’ll have a healthy forest. But we don’t actually know that because there isn’t any long-term experimental evidence with sufficient replication and controls available in the public domain,” she says.
Dense planting puts stress on groundwater
The Miyawaki method typically involves planting around 340 native saplings in a dense arrangement, spaced just two to three feet apart. For the Bengaluru plantation drive, the BDA selected more than 350 native species, including Indian banyan (Ficus benghalensis), Mysore fig (Ficus drupacea), white fig (Ficus virens), neem (Azadirachta indica), Indian beech tree (Pongamia pinnata) and many fruit trees.
Ecologists caution that using native species alone does not guarantee ecological restoration. Bengaluru’s landscape is not a rainforest but a mosaic of granite outcrops, dry tropical forests, thorn scrub and semi-arid savannas. In a seasonally dry city already grappling with groundwater depletion, dense, water-intensive plantations can place additional pressure on limited water resources, argue ATREE’s Abi T. Vanak and Adithya in a recent commentary.
“We need to plant trees that conserve water. In Bengaluru’s climate, what is required are savanna plants,” says Goswami. His team is restoring remnant savanna patches in Bagepalli, about 100 kilometres north of Bengaluru, where ecological conditions resemble those that once existed around the city. Dominated by species such as babul (Acacia nilotica), wild jujube (Ziziphus numularia) and palash (Butea monosperma), these grass-rich ecosystems support birds including laughing dove, rufous-tailed lark, Jerdon’s bushlark, chestnut-bellied sandgrouse and sirkeer malkoha, all well adapted to semi arid open savannas.
Ultimately, the debate is about rethinking what restoration should look like in cities. “Urban restoration needs to be approached differently because cities are already heavily modified landscapes often with space and water constraints,” Choksi says. Rather than attempting to recreate dense forests everywhere, restoration should respond to local ecology while also meeting people’s needs for shade, recreation and accessible green spaces.
She adds: “The challenge is to find a balance between biodiversity and people’s needs for recreational spaces. For a city like Bengaluru, that might mean relatively low-density tree planting combined with the restoration of native grasses and shrubs. We should allow these spaces to remain a little wild, instead of always thinking of highly manicured, walkable landscapes.”
Urban restoration should combine trees with grasses, shrubs and other native vegetation, involve local communities in planning, and recognise that different landscapes require different restoration approaches. “We need trees,” Choksi says, “but we need other kinds of vegetation too.”
Banner image: A blackbuck at the restoration site in Bagepalli. Image courtesy of ATREE.