The monarch butterfly has grown closer to extinction after it was classified as endangered.
The International Union for the Conservation of Nature added the butterfly to its 'red list' of threatened species and categorised it as 'endangered' which is only two steps from extinction, Associated Press reported.
The North American butterflies are estimated to have suffered a decline in population between 22 percent and 72 percent over the last 10 years, depending on what method of measurement was used.
Conservation biologist Nick Haddad said they are concerned about the rate the insects are declining.
"What we're worried about is the rate of decline. It's very easy to imagine how very quickly this butterfly could become even more imperilled."
Haddad estimated the population of the butterflies he has studied in the eastern United States has declined between 85 percent and 95 percent since the 1990s, Associated Press reported.
Non-profit Xerces Society's Emma Pelton said the decrease in population was because of the loss of habitat and increased use of herbicides and pesticides for agriculture, as well as climate change.
"There are things people can do to help," she said, including planting milkweed, a plant that the caterpillars depend upon.
The United States has not listed monarch butterflies under the Endangered Species Act, but several environmental groups believe it should be listed.
