UGIINUUR, ARKHANGAI PROVINCE, MONGOLIA — The endless grassland has become a sieve, dotted with what look like golf holes. Small gray rodents move in and out, increasing in number as the late autumn sun warms the Mongolian steppe in the central Khangai region.

Munkh-Erdene Baasanjav, a shepherd for 30 years, drills a hole in a raised mound and puts his hand in it to confirm his fears: a nest of thick grass. After removing the material, he pumps 60 liters of water down the hole, an environmentally friendly method of freezing the creatures.

“When I was a kid, there were rodents in some places, but now they’re scurrying around like rising dust,” he says.

The pests are Brandt’s voles, one of the fastest breeding mammals in the world. Female voles can give birth three times a year, up to 11 young each time. Just one of these rodents, smaller than a human hand, can eat 34 grams (1 ounce) of grass a day and store 9 kilograms (20 pounds) of hay for the winter.

Rising temperatures and overgrazing in Mongolia have fueled a dramatic increase in the vole population, making soil conditions more favorable for nesting. The infestation threatens a third of the country’s grasslands (38.6 million hectares or 149,000 square miles), according to the Ministry of Food, Agriculture and Light Industry, leaving less food for the livestock. Terriers also present a hazard, leading horses and people to sprain ankles or break bones. In response, ranchers and government rangers are working to reduce the vole population without harming other animals.

Enkhbold Nanj, a doctor of biological sciences at the Plant Protection Research Institute, a national organization that studies Mongolia’s grasslands and pests, says it’s normal to have 100 voles per hectare, but some regions now have as many as 2,000. Estimates place their total population at over a billion.

“It’s too much,” he said. “It flips the ground.”

Mongolian grasslands are owned by the state, while cattle are owned by the private sector. A pillar of the economy, the livestock sector represents more than 10% of the country’s gross domestic product and 23% of its working population. Herders raise horses, cattle, sheep, goats and camels and earn money by selling dairy products, meat and hides.

Since the country’s transition to a market economy, the number of livestock heads has almost tripled, from 25 million in 1990 to almost 70 million in 2020. The resulting overgrazing has caused soil deterioration on 78% of its grasslands, according to the Mongolian National Federation of Pasture User Group, an autonomous association of more than 80,000 members working to develop pasture management policies.

Dr Tseveendorj Dalkhaa, head of the Rodent Research Laboratory at the Plant Protection Research Institute, says humans must accept responsibility for disturbing the ecosystem by chasing or chasing the vole’s natural predators, such than foxes.

“If an animal exists in nature in a balanced way, it will cause no harm,” he says. “But voles are said to be harmful when the right balance is lost.”

The average temperature in Mongolia has risen more than 2 degrees Celsius (over 3.5 degrees Fahrenheit) since 1939. Combined with overgrazing, the resulting dry, hot soil has created a favorable environment for voles to multiply, says Munkhnasan. Tsevegmed, pasture protection. and Catering Specialist at the Ministry of Food, Agriculture and Light Industry.

Prior to 2003, Enkhbold says the Mongols used pesticides to protect pastures, but these chemical methods were abandoned due to their toxic environmental impacts.

Traditional extermination methods are much more labor intensive. Since 2019, the government has given a daily bonus of 2,000 Mongolian togrogs (70 cents) to herders and 20,000 togrogs ($7) to the unemployed who pour water into burrows, spread rice contaminated with killer bacteria voles and provide shelter for birds of prey. .

These organized efforts have so far been deployed across 15% of the affected region, says Munkhnasan, which is not enough to overtake the vole’s breeding success or address the root causes of the infestation.

Enkhtur Badam-Ochir, a 41-year-old shepherdess from soum or Ugiinuur district, says when she weighed a year-old sheep for sale five years ago, it weighed 21 kilograms (46 pounds). Today, she says, the same sheep would weigh no more than 18 kilograms (40 pounds).

“Voles eat all the tasty and nutritious grass,” says Enkhtur. “Therefore, the animals do not get fat.”

Local and national levels of government are focused on tackling the vole problem. As provincial governors adjust pasture use plans by consulting local herders and taking into account annual plant yields, the Ministry of Food, Agriculture and Light Industry is working to regulate the use and protection of land on a national scale. This includes a livestock tax law, which took effect in July 2021, which uses the revenue to fund more pest control efforts and rehabilitate the country’s grasslands.

“The most affordable, effective and sustainable measure to regulate excessive vole breeding is to reduce overgrazing and allow vegetation to regrow,” says Munkhnasan.

The number of cattle heads should reflect the size of pastures, and the economic turnover of cattle should accelerate, he said. And breeders should have fewer high quality animals, rather than a lot of low quality animals.

Although they recognize the problems of overgrazing, many Mongols cannot afford to reduce their herds.

“We provide all our livestock needs, and the price of raw materials is not enough, so we don’t want to reduce the number of livestock,” says Munkhtsetseg Tudev, a resident of Ugiinuur soum. Less livestock, she says, “isn’t enough to live on.”