Photo taken on Jan. 2, 2021 shows the coffee tree at Haikou Tropical Agricultural Science And Technology Expo Park in Haikou, south China's Hainan Province. Haikou Tropical Agricultural Science And Technology Expo Park was opened here Friday. (Xinhua/Pu Xiaoxu)

Photo taken on Jan. 2, 2021 shows the soilless vegetables at Haikou Tropical Agricultural Science And Technology Expo Park in Haikou, south China's Hainan Province. Haikou Tropical Agricultural Science And Technology Expo Park was opened here Friday. (Xinhua/Pu Xiaoxu)

Photo taken on Jan. 2, 2021 shows Haikou Tropical Agricultural Science And Technology Expo Park in Haikou, south China's Hainan Province. Haikou Tropical Agricultural Science And Technology Expo Park was opened here Friday. (Xinhua/Pu Xiaoxu)

People visit Haikou Tropical Agricultural Science And Technology Expo Park in Haikou, south China's Hainan Province, Jan. 2, 2021. Haikou Tropical Agricultural Science And Technology Expo Park was opened here Friday. (Xinhua/Pu Xiaoxu)

Photo taken on Jan. 2, 2021 shows the pitaya at Haikou Tropical Agricultural Science And Technology Expo Park in Haikou, south China's Hainan Province. Haikou Tropical Agricultural Science And Technology Expo Park was opened here Friday. (Xinhua/Pu Xiaoxu)

People visit Haikou Tropical Agricultural Science And Technology Expo Park in Haikou, south China's Hainan Province, Jan. 2, 2021. Haikou Tropical Agricultural Science And Technology Expo Park was opened here Friday. (Xinhua/Pu Xiaoxu)

Photo taken on Jan. 2, 2021 shows Haikou Tropical Agricultural Science And Technology Expo Park in Haikou, south China's Hainan Province. Haikou Tropical Agricultural Science And Technology Expo Park was opened here Friday. (Xinhua/Pu Xiaoxu)

Photo taken on Jan. 2, 2021 shows Haikou Tropical Agricultural Science And Technology Expo Park in Haikou, south China's Hainan Province. Haikou Tropical Agricultural Science And Technology Expo Park was opened here Friday. (Xinhua/Pu Xiaoxu)

Photo taken on Jan. 2, 2021 shows the brunfelsia acuminata at Haikou Tropical Agricultural Science And Technology Expo Park in Haikou, south China's Hainan Province. Haikou Tropical Agricultural Science And Technology Expo Park was opened here Friday. (Xinhua/Pu Xiaoxu)

A man visits Haikou Tropical Agricultural Science And Technology Expo Park in Haikou, south China's Hainan Province, Jan. 2, 2021. Haikou Tropical Agricultural Science And Technology Expo Park was opened here Friday. (Xinhua/Pu Xiaoxu)

Photo taken on Jan. 2, 2021 shows the adenium obesum at Haikou Tropical Agricultural Science And Technology Expo Park in Haikou, south China's Hainan Province. Haikou Tropical Agricultural Science And Technology Expo Park was opened here Friday. (Xinhua/Pu Xiaoxu)

Photo taken on Jan. 2, 2021 shows the crab cactus at Haikou Tropical Agricultural Science And Technology Expo Park in Haikou, south China's Hainan Province. Haikou Tropical Agricultural Science And Technology Expo Park was opened here Friday. (Xinhua/Pu Xiaoxu)

Photo taken on Jan. 2, 2021 shows Haikou Tropical Agricultural Science And Technology Expo Park in Haikou, south China's Hainan Province. Haikou Tropical Agricultural Science And Technology Expo Park was opened here Friday. (Xinhua/Pu Xiaoxu)