Tropical rainforests are the cradle of life (perfect conditions for life) on Earth, i.e., rich in plant species composition (>250 plant species/hectare) and fauna diversity (>50% of animal species in the world). Rainforests occur near the Earth’s equator and cover 6% of the Earth’s surface across the tropical regions and are characterized by wet climate, i.e., heavy rainfall (125—660 cm), relative humidity (77—88%) and temperature (20—34°C). They are dominated by a wide range of broad-leaved trees that form dense canopy and the most complex ecosystem. Currently, the tropical rainforest ecosystem is changing faster than ever in human history due to anthropogenic activities, such as habitat loss and degradation due to deforestation for timber and conversion into agriculture fields (oil palm plantation), mining, fire, climate change, etc. The habitat loss and degradation had adversely influenced the distribution and richness of the fauna species. The current information on the fauna diversity of tropical rainforest is not sufficient and in the future, more research is required to document the various community parameters of the fauna species in order to conserve and protect them. For better future, conservation, and management, we must identify the major drivers of changes and how these factors alter the tropical rainforest.
Tropical rainforest usually occurs 10° north and south of the equator, where climate conditions are unique such as humid, warm, and wet. The monthly mean temperature is 18°C and the annual rainfall is not less than 168 cm. Tropical rainforest occurs in four main regions; Central and South America, Central and West Africa, Indo-Malaya and Australia . They are storehouses of a range of food resources for a wide variety of fauna species as well as for human beings, raw material for buildings, and medicines and affect the climate.
1.1. Ecological importance of tropical rainforest
Tropical rainforests are the most diverse in the vegetation structure and composition that supported a diversity of fauna species such as birds, reptiles, mammals, amphibians, and invertebrates, which directly or indirectly depend on them for their survival and existence. They are rich in habitat diversity and provide a variety of resources for the avian species, such as food, habitat, and shelter . Tropical rainforest is vital ecosystem, i.e., it provide crucial ecosystem services such as raw materials, reservoirs of biodiversity, soil protection, sources of timber, medicinal plants, carbon sequestration, and watershed protection.
1.2. Threats to tropical rainforest
Tropical rainforest covers less than 10% of the land area of the Earth, representing the largest biological diversity reservoir, i.e., >50% of known plant species grow in tropical rainforest. Despite being rich in fauna diversity, every year, huge areas of tropical rainforests are being lost and degraded due to human interference. It has been stated that 25–50% of the world’s tropical rainforest has been lost and degraded due to the land–use change such as deforestation for palm oil plantations, agriculture expansion, cattle ranches, mining, and development of housing societies, while the rest of the rainforest areas is under a major shift in the dynamic structure and productivity.
It has been reported that Southeast Asia had the highest rate of land-use change (such as deforestation of tropical rainforest for conversion into oil palm plantation, commercial logging for timber and development of human settlement) as compared to other regions. Deforestation and fragmentation due to agriculture expansion, human settlement, logging, and fire had altered the plant species composition, richness, and diversity. Deforestation and fragmentation, over-exploitation, invasive species, and climate change are the major factors due to which the biodiversity of tropical forest had declined at an alarming rate. For example, some of the fauna species became extinct, while others became threatened and vulnerable due to habitat loss, fragmentation, and degradation.