There are more than 500 kinds of deltas, which also reflect the characteristics of tropics. They belong to 130 families and 373 genera (Chen Shupei, 1984), among which pure tropical genera account for 42% and even pantropical genera account for 53%. Tropical genera account for 62% and tropical species account for 56% in Dinghushan area, namely 129 1 species. Among the genera of Luofushan 146, the pantropical genus accounts for 9 1% (Zheng Zhiqing, 1987). Evergreen vegetation in monsoon forest is mostly geomantic forest and miscellaneous forest, mostly secondary, which is mainly tropical flora (Wang Zhuhao, 1982) with a small area. Most of the hills on the platform are evergreen shrubs. Grass slope with tropical elements is prone to soil erosion because it grows on latosol soil layer. Insect-eating plants such as Nepenthes are tropical plants. The ecological characteristics of tropical plants are also fully reflected in common cultivated trees. For example, on banyan trees, roots of boards, roots of air and roots of columns can be seen, which can grow into forests by themselves. Flowering on the old stems can be seen in carambola and pineapple. Annual flowers are found in Prynne and Hibiscus; The leaves of pliers exist in mangoes; Rotting leaves exist in mangoes and lychees; Drip-pointed leaves are found in bodhi trees. The ecological characteristics of these tropical plants are consistent with the distribution area of tropical monsoon rain forest here. Among them, Aquilaria sinensis (Aquilaria sinensis) was widely planted in Dongguan County in the Ming Dynasty and became a famous product in Dongguan, known as "Vientiane". This shows that the Pearl River Delta is a tropical delta. Also, correspondingly, there are also large tropical animals inhabiting the delta region, although they have been hunted down by people today, such as the rhinoceros recorded in the hilly area of Dongguan.
Delta is a water network area, dominated by swamps, depressions and low-lying forests, so it is also home to many typical tropical giant animals, which also reflects the original tropical characteristics of the delta. Such as Asian elephants, Malay crocodiles, peacocks, etc. There are many descriptions in ancient books, even with fossils as evidence. For example, during the Three Kingdoms period, crocodiles were still growing in Guangzhou. Water mirror Nott said: "The giant crocodile is a rare and strange thing, there are thousands of kinds, I can't remember." Today, Pingzhou fishermen also extracted crocodile skulls from the river, indicating that there are crocodiles in Guangzhou. There are also crocodile skeletons unearthed in Shunde and Xinhui. The (Tangxia) 14C of Dalin is 3020 80, and that of Liu Le is 2540 105. There are also records of elephants harming crops in Nanhan, Dongguan. The author once collected the tibia of an elephant in the mud layer of Guxihu District, Guangzhou. The Annals of the South China Sea (Yuan Dynasty) still records the existence of elephants. There are records of Peacock in Kaiping in Jin Dynasty and Xinhui in Tang Dynasty. It can be seen that the Pearl River Delta has been a place where tropical animals are distributed since ancient times, in which ivory is hunted and used as a commodity. The Tang Dynasty's "North Household Record" contains: "The teeth are small and red, comparable to cutting, not inferior to imported ones." Crocodiles are recorded as eating people and animals, which is very different from Chinese alligators in the Yangtze River, and is consistent with porous crocodiles and crocodiles. In today's Nanyang Islands. Elephants are Asian elephants. Today, due to the continuous development of the delta, the increase of population and the destruction of trees, they have been hunted to death.
From the analysis of geographical environment such as landform, climate, hydrology, vegetation and animals, the Pearl River Delta is a tropical delta, which is different from the Yellow River Delta and the Yangtze River Delta. Geomorphology and hydrology show a good water network with many branches and many wide deep-water rivers. The climate is rich in heat and radiation; Vegetation grows vigorously, with many kinds and animals, which is very beneficial to industrial and agricultural production. In terms of types, the Pearl River Delta is similar to tropical deltas such as the Red River Delta and Mekong Delta. In view of the scarcity of tropical areas in China, we should give full play to the tropical characteristics and potential of the Pearl River Delta.