The change in the global climate cause global warming where increase in global temperature by 1.5°C in a year is no longer impossible but an urgency that needed drastic measures to prevent it from happening (IPCC,2018). The increase in population growth comes with the increase of land use for built space and decrease in green infrastructure and landscape, hence cause climate change. Therefore, environmental and ecological problems will likely arise due to the climate change, thus forest ecosystems play an important role in mitigating the impact of global warming as it is one of the major contributors of global ecosystem carbon pools (Watson, 2000). Protection and rational utilization of natural resources become more and more important whereby forests are important not only as source of wood but as the means of protecting the hills. With accurate estimation of forest biomass carbon sinks, it will help in improving the understanding of carbon cycle (Zhao et al., 2019) and armed us in facing the climate change with holistic sustainable forest management policies developed from the knowledge gained.
The unceasing increase of carbon dioxide emission from moving vehicles fuels by fossil fuel and power automobiles, deforestation, buildings, industry development, pollution and more has cause the increase of the greenhouse gases and excessive heat in the earth’s surface, thus powering the global warming and climate change. Due to the awareness to manage carbon emission, Kyoto Protocol 1997 were developed by the United Nations (UN) that aim to reduce anthropogenic greenhouse gases. According to the World Bank (2010), and Chen and Chen (2012), 70–80% of standard global carbon emissions are generated from economic activities and urban areas and the numbers are increasing every year. In order to minimise the increase of carbon dioxide emission, the benefits of trees should be derived in this situation as trees have the potential and capability of carbon storage (Yunusa and Linatoc, 2018). Trees acts as a sink for carbon dioxide by absorbing carbon during photosynthesis and storing carbon as biomass. During the growing period of a tree, it stores carbon, therefore, affect surrounding climate, carbon cycles, air temperature and alter the carbon emission of the surrounding area (Alamgir and Al-Amin, 2007).
More trees are needed in area where abundant carbon dioxide is released such as in urban and city areas that usually heavily populated. The type of forest that usually found in urban cities are usually secondary type of forest. It is also known as urban forest. Rapid urbanization and industrial development caused the formation of secondary forest especially in developing urban centres due to the anthropogenic pressure and population migration to urban centres (Ngo et al., 2013). Although secondary forest is closer to human territory and act as carbon reservoir, primary forest is still the best option in managing carbon cycle in an ecosystem compare to secondary forest. A large healthy tree in cities is estimated to remove as much as 60 to 70 times the quantity of air pollution compared to new planting (McPherson et al., 1997). Failure to provide the optimum condition necessary for trees to grow and mature in city area will affect the full ecological and aesthetic potential of trees in the city (Trowbridge and Bassuk, 2004, Milward and Sabir, 2010). Hence, the amount of carbon sequenced and absorbed is greater with primary forest compared to secondary forest as the trees’ growing condition and environment are usually disturbed by the rapid development of the city.
Urban forest usually designed and managed to be ecologically, socially and economically sustainable (Thompson, Pillsbury and Hanna, 1994). Despite knowing the benefits of urban trees towards environmental, human health and aesthetic benefits, it still faces threats from the rapid urban development population growth such as disease, unsatisfactory soil conditions, vandalism, pollution, and increase in land use. Trees have it hard to survive especially in the harsh urban environment.
Without forest inventory, forest management would not be sustainable and benefits to people and environment but with forest inventory, a proper management of the forest can ensure a functional urban ecosystem including improved public health, cleaner air, cool local air temperatures, filter and retain storm water management, sequester carbon, and aesthetic value for the community (Dwyer, Schroeder and Gobster, 1991; Dwyer and Schroeder,1992; McPherson et al., 2005; Nowak et al., 2008; McPherson and Simpson,2003). In order to maximize these environmental services, it requires decision-making that is grounded by up-to-date inventory of the forest’s trees (Millward and Sabir, 2010). Initiative to implement green infrastructure within urban and cities such as tree planting campaign can help in mitigating the environmental effect of urbanization (Young, 2013). Lottrup (2013) in his study mentioned that people living and working near to green outdoor environment help in reducing stress and healthier.
Forest inventory is one of such tools and by using the correct sampling technique, less error can be done and avoided. Usually, vital information obtained from forest inventory that is very useful for forest management are growing conditions, volume of trees, stock resources, resource planning, annual growth and net worth statement, forest composition and topography, wildlife population, tourism potentials, hydrology, species, carbon sequestration and the non-timber forest products assessment (NTFP) (Wenger, 2013). Hush et al. (1972) in his study mentioned forest inventory as a procedure to obtained information on the quantity and quality of the forest resource and other characteristics of the trees in the forest while they grow. Correct and effective sampling technique is the most important data that need to be collected in forest inventory to establish a proper and holistic forest management. Sampling design can be classified into two groups: probability and non-probability sampling. Both sampling groups apply statistical sampling theory and obtained unbiased estimates of the sampling errors. In short, the benefit sampling are such time and money efficiency, less labour, and more ease and accurate measurements. With good and reliable data from forest inventory, better forest management can be done in order to produce excellent goods and services from the forest. According to Adekunle (2011), there are four ingredients for the recipes of effective sampling techniques for forest management. The first ingredient is to use accurate statistical and computational tools to analyse data collected during forest inventory. The second ingredient is acquiring well experienced and knowledge personnel to monitor and exercise during the data collection and processing. The third ingredient is to be well equipped in terms of equipment, logistics, facilities, etc. during data collection and processing. The last ingredient is to have proper storage and retrieval systems of the information and data gathered for reporting purposes.
Sustainable forest management (SFM) addresses great challenge to match the increasing demand of growing human population while maintaining the ecological function of the forest ecosystems (MacDicken et al., 2015). It also helps in addressing forest degradation and deforestation while increasing direct benefit to people and the environment. The results obtained from forest inventory play an important role in providing data for planning, monitoring, evolution, research, growth and holistic framework of a forest. Since the past decades, sustainable forest management has become a global highlight due to the increase in overexploitation of the forest (Power, 2001; Robert, 2003) and causing climate change that effect mankind (Schwalm and Ek, 2001). SFM is difficult to define and there is no universally agreed-on definition (Dau, Mati and Dawaki, 2015).
Globally, forest management related policies are reported being executed on 97% of global forest area. Due to the increase in forest management, the numbers of countries with national forest inventories have increased over the past 10 years from 48 to 112 countries (MacDicken et al., 2015). In 2010, the percentage of the forest with management plans globally increase dramatically by 70% since 1950s. Many countries in the world are competing with each other to achieve sustainable forest management by reporting data that suggest they are moving towards sustainable management goals (Siry et al., 2005). Thus, a sound forest inventory is a vital tool in gathering information to manage forests and its resources towards sustainable ecosystems of the environment and mankind.