File photo taken on July 23, 2016 shows two wildebeests battling with each other at the Maasai Mara National Reserve, Kenya. The International Day for Biological Diversity falls on May 22. (Photos: Xinhua)

An impala is seen at Nairobi National Park in Nairobi, capital of Kenya, May 19, 2021. The International Day for Biological Diversity falls on May 22.

A lion is seen at Nairobi National Park in Nairobi, capital of Kenya, May 19, 2021. The International Day for Biological Diversity falls on May 22.

An ostrich is seen at Nairobi National Park in Nairobi, capital of Kenya, May 19, 2021. The International Day for Biological Diversity falls on May 22.

A lion is seen at Nairobi National Park in Nairobi, capital of Kenya, May 19, 2021. The International Day for Biological Diversity falls on May 22.

Two zebras are seen at Nairobi National Park in Nairobi, capital of Kenya, May 19, 2021. The International Day for Biological Diversity falls on May 22.

Hippos are seen in the water at Nairobi National Park in Nairobi, capital of Kenya, May 19, 2021. The International Day for Biological Diversity falls on May 22.

Gazelles are seen at Nairobi National Park in Nairobi, capital of Kenya, May 19, 2021. The International Day for Biological Diversity falls on May 22.

Antelopes are seen at Nairobi National Park in Nairobi, capital of Kenya, May 19, 2021. The International Day for Biological Diversity falls on May 22.

Buffaloes walk through arches of a bridge at Nairobi National Park in Nairobi, capital of Kenya, May 19, 2021. The International Day for Biological Diversity falls on May 22.

An antelope is seen at Nairobi National Park in Nairobi, capital of Kenya, May 19, 2021. The International Day for Biological Diversity falls on May 22.

A starling is seen at Nairobi National Park in Nairobi, capital of Kenya, May 19, 2021. The International Day for Biological Diversity falls on May 22.

File photo taken on Sept. 26, 2019 shows flamingoes foraging at beach in Namibia. The International Day for Biological Diversity falls on May 22.

File photo taken on Oct. 24, 2020 shows a kudu at the Save Conservancy in Masvingo province, Zimbabwe. The International Day for Biological Diversity falls on May 22.

Impalas are seen at Nairobi National Park in Nairobi, capital of Kenya, May 19, 2021. The International Day for Biological Diversity falls on May 22.

A buffalo is seen at Nairobi National Park in Nairobi, capital of Kenya, May 19, 2021. The International Day for Biological Diversity falls on May 22.

File photo taken on Oct. 24, 2020 shows kudu at the Save Conservancy in Masvingo province, Zimbabwe. The International Day for Biological Diversity falls on May 22.

File photo taken on June 5, 2020 shows white rhinoceros at the Thetford Conservancy near Harare, capital of Zimbabwe. The International Day for Biological Diversity falls on May 22.

A giraffe forages at Nairobi National Park in Nairobi, capital of Kenya, May 19, 2021. The International Day for Biological Diversity falls on May 22.

Gazelles are seen at Nairobi National Park in Nairobi, capital of Kenya, May 19, 2021. The International Day for Biological Diversity falls on May 22.

Buffalos forage at Nairobi National Park in Nairobi, capital of Kenya, May 19, 2021. The International Day for Biological Diversity falls on May 22.

File photo taken on Nov. 29, 2018 shows an elephant drinking water at Tsavo National Park, near Voi, Kenya. The International Day for Biological Diversity falls on May 22.