When botany professor Bharat Babu Shrestha visited Nepal’s Chitwan National Park in 2013, feverfew – a flowering plant in the daisy family – was rare. Today, large areas of the park’s grasslands are covered in the invasive plant, said Shrestha, who teaches at Tribhuvan University on the outskirts of Kathmandu.
Non-native plants have been spreading fast in Nepal’s oldest national park in recent years – and part of the reason is rising temperatures as fossil fuel use heats up the planet, said the expert in “invasion ecology”.
“The changing climate appears to be conducive for invasive alien plants to grow faster,” Shrestha said.
The surge in alien plants in Chitwan, a 950-sq-km park in Nepal’s southern plains, is now crowding out grasslands and wetlands that provide food and shelter for the park’s iconic wildlife, say park authorities.
It’s a problem seen in parks and reserves around the world as climate change shifts what it means to “conserve” natural areas.
“Like never before, the park faces habitat loss at an alarming rate,” said Ananath Baral, chief conservation officer at Chitwan. “We are concerned about the wildlife’s future.”
In the past decade, the park’s grasslands have been heavily invaded by plants such as feverfew, lantana, a vine known as “mile-a-minute” weed – and Siam weed, considered one of the world’s most problematic invaders, Baral said.
As a result, in some parts of the park, the grass favoured by the park’s wildlife – including the one-horned rhino, deer and antelope – has partially or totally disappeared, he said.
Chitwan’s most recent grassland mapping, published in 2016, shows the area of the park and its buffer zone covered by grass has shrunk to 6%, down from 20% in 1973 when the reserve was established. Both rising temperatures and more erratic rainfall have allowed non-native plants to thrive, said Uttam Babu Shrestha, who has looked at invasive species in Chitwan as director of the Kathmandu-based Global Institute for Interdisciplinary Studies.
With global temperatures predicted to keep climbing as the world struggles to curb use of fossil fuels, “plant invasion is likely to increase in the near future”, he warned.
Like the grasslands, the park’s wetlands also are under stress: covered by plants that the local wildlife do not eat and squeezed by unprecedented floods and unpredictable droughts, biologists say.
Babu Ram Lamichhane, head of the Biodiversity Conservation Center in Sauraha, at the gateway to Chitwan, said the combination of intense rain with flash floods in the monsoon season and prolonged dry spells in the spring are degrading Chitwan’s wetlands.