## 1 Introduction  
The loss and degradation of the world's forests are major contributors to biodiversity loss and climate change [1]. Forests occupy the largest plant community on the land surface of the Earth, sequestrate most of the atmospheric carbon [2], are an overall sink of \(-2.1\) Gt CO\({}_{2}\) per year [3], and, hence, play a pivotal role in the global carbon cycle [4]. Tropical ecosystems span over \(\sim 33\%\) of the global land area [5] and are the major contributor of global CO\({}_{2}\) sink. The tropical forests occupy 45% (1.827 billion ha) of the total global forests (4.06 billion ha) [6]. These forests contribute 56% (1.4 billion metric tons) of the terrestrial absorption of atmospheric CO\({}_{2}\)[7] at an annual rate of 1.3 PgC [8]. Tropical forests are also acknowledged for providing important ecosystem services, including biomass production, carbon stock, carbon sequestration (or fluxes) and global and regional climate patterns [9]. Collectively, tropical forests provide 50% of the total plant biomass of the Earth [10], and are renowned as \"the lungs of the planet Earth\" due to their role in the exchange of gasses, particularly inhaling CO\({}_{2}\) and breathing out O\({}_{2}\), within the atmosphere [11]. Tropical forests are dynamic ecosystems that undergo successional changes [12; 13], natural disturbances, deforestation and land degradation [14]. Recent evidence from a detailed time series of satellite images indicates a 62% increase in deforestation in the humid tropics from the 1990s to the 2000s [15]. A broad outline prediction of the future of tropical forest indicates extensive agricultural encroachment into the old-growth forest due to an expected 2 billion increase in the population of tropical countries over the next few decades [16]. However, the recent Forest Recourses Assessments (FRA) by the Food and Agriculture Organization (FAO) [6], reported a 32% reduction in an annual deforestation rate of tropical forests from the 1990s to the latter half of the 2020s. On the other hand, secondary succession has regained 15% of the area deforested during the 1990s, as a result of millions of hectares of the tropical landscape being abandoned following massive deforestation and large-scale agricultural activities [17]. Knowledge of accurate and up-to-date forest inventories, recovery rates and variation in regrowth rates across time and space is mandatory in facilitating well-informed management, and in understanding biomass and carbon sequestration potential of these dynamic ecosystems to mitigate future climate change impacts reducing the uncertainties in estimating global carbon flux. However, it is difficult to ascertain structural characteristics of these difficult-to-access ecosystems through conventional field-based inventories, as the tropical forests are composed of a variety of species with high structural and biological diversity varying along with spatial and temporal scales [18]. Field-based carbon stock inventories of the huge tropical forest area (approximately 18 million km\({}^{2}\)) are logistically challenging, time demanding and difficult to repeat over time to monitor the growth. Existing long-term and short-term field plots in the tropical forest provide invaluable information about forest functions and attributes, but are too small in terms of numbers to fully represent the dynamics of tropical systems and carbon stocks [18]. Rapidly developing space-borne and air-borne remote sensing technologies and tools are increasingly used to obtain quick, reliable and consistent information over large areas [19], complementing less frequent and spatially limited field inventories, to understand tropical forest ecosystem function, structure, and productivity, and to record changes in the forests' attributes (e.g., leaf area structure, basal area, stem volume, and basal-area weighted mean diameter and basal-area weighted mean height) at varying spatial and temporal scales [20].