// NATURE NEWS — SPAZIO & SCIENZA
When humans disappear, biodiversity takes a surprising turn
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Life-sized puppets in a remote village in Japan symbolize depopulation in the country. Credit: Buddhika Weerasinghe/Getty
Less than an hour’s train ride from central Tokyo, ecologist Kei Uchida walks through glades of mountain cherry trees and meadows filled with susuki grass as tall as an elephant. The researcher smiles when he spots something by the trail: a tangled orb of grass stalks, at about knee height. It is the nest of the tiny Eurasian harvest mouse (Micromys minutus), a species that has been on the decline in this area and has been targeted for protection.
Volunteers saved this location around Mount Tenran from development 30 years ago, and today they monitor its plants and animals, thin its forests and even plant and harvest rice — all in the name of biodiversity. Here, nature needs people. In the shallow water of the rice paddy, fish as small and arched as an eyebrow swim, and just above the water’s surface, dragonflies mate. At dusk, fireflies dance above the fields.
Uchida, an environmental scientist at Tokyo City University in Yokohama, and his colleagues included this site in a study of thousands of species in more than 150 wooded, agricultural and ‘peri-urban’ landscapes in Japan1. Unsurprisingly, they found that the diversity and abundance of most species declined at sites where the human population was growing. But they also found that biodiversity declined in places where the number of people was decreasing (see ‘Lost life’). This result — and others like it in different parts of the world — contradicts the common assumption that when people leave, nature always thrives.
Japan and many other nations are seeing a vast emptying of rural areas as people flock towards urban centres. Studies2 are showing that this can have a detrimental effect on biodiversity in the depopulated areas, which creates new challenges. Rather than simply setting up and managing protected areas, conservation officials must consider whether and how to recruit, train and support people to be permanent parts of some ecosystems.
I’ve joined Uchida and local volunteers to learn more about how human activity can increase biodiversity. Uchida says that this area is a typical satoyama landscape — a term that combines the words for village and mountain. “Agriculture and living things can coexist,” Uchida says. But Japan’s satoyama are being lost to depopulation and urbanization.
In this area near Mount Tenran, as in many woodlands across Japan, humans spent centuries cutting trees for fuel and removing fallen leaves for fertilizer. That opened up the forest and benefited specific plants and insects. But when that activity stopped, the forest became dense and closed in again. “We have used the woods for 1,000 years, but not lately,” Uchida says. Now, young students are being given small handsaws and taught the centuries-old art of woodland thinning.
Kojima Tsubasa, a volunteer nature monitor, shows me where he sits in the evenings to count fireflies. There are two types here: the smaller heike fireflies (Aquatica lateralis), which prefer rice fields; and the larger, brighter genji fireflies (Nipponoluciola cruciata), associated with running streams. “It’s rare to see both at once,” he says, proudly. Four days ago, Tsubasa says, he counted 60 fireflies at this paddy. Often, he is not alone. Japanese urbanites, yearning for the charm of the countryside, come here to watch the fireflies at dusk. But after the show, they get on the train and return to the brighter lights of Tokyo.
Most Japanese people now have to travel to see fireflies — whereas once the insect’s bright beauty was right outside their homes. It’s a trend seen the world over. As recently as 1950, nearly 40% of the global human population lived in the countryside. According to United Nations data, just 19% of the world’s 8.2 billion people now live in rural a