2.1. Conceptual Review.
Infrastructures, in the views of (Buhr, 2009; Fasoranti, 2016; Regan, 2017 and Losos, Pfaff, Olander, Mason, and Morgan, 2018) are a set of heterogeneous, essential, hard and soft, social and economic assets. They are characteristically intangible, physical but capital intensive public goods of long life cycle (Flyvbjerg, 2014; Iyortyer, 2017) and factor inputs of overall modern economy, long-term capital appreciation, welfare especially in the developing economies. Putten (2016) and (Chakrabarti, 2018; World Bank. 2019) argued that though infrastructures deﬁne economy of economies but recognized possible hindrances and constraint to ambitious infrastructure investment and growth as range of associated environmental and ﬁnancial concerns, geopolitics, public policy, socio-cultural spatial linkages, etc.
The environment substantially supports human life and living activities that promote growth but is vulnerable to intensive and extensive risks e.g., pollution (air, water, soil and radioactive) (Ohiare, 2015). However, some alternative routes and attempts are being developed to reduce these environmental risks and its economic consequences such as, exploring renewable energy sources, encouraging green housing construction methods and materials, developing electric-powered transport system, improving road networks and trafﬁc etc, according to (Olanipekun 2016; Losos et. al., 2018; Meng and Han, 2018 Li, Deng, Zhang, Olanipekun and Lyu, 2019).
Though economic growth has been severally construed (Adelakun, 2011: Fasoranti, 2016; Edeme, 2018) but central to the views that economic growth is the sustained and greater increase in output ( or income) as a derivative of efficiency and amount of inputs factors in an economy over a long time period usually expressed in Gross Domestic Product (GDP). The changes in nominal Gross Domestic Product (GDP) from one year to the next across all economic sectors expressed in percentage reflects economic growth rate and serves as common bases for measuring performance and strength of nation’s economy (Fasakin and Jegede, 2018). For example, the Nigerian economy grew at an average of 2.45% GDP between (years 1999-2017), specifically with 5.52% GDP in year 2000, 6.8% GDP in 2005 through 9.54% in 2010 but slowed to 2.79% (in 2013) and contracted by -1.5% in 2016 (NBS, 2016) but recovered with average of 1.95% since 2107/2018 fiscal years (NBS, 2017). Economic growth accounting includes intensity and scale of infrastructures spending but largely exclude production from the informal market and environmental vulnerabilities etc., in Nigeria ((Babatunde, 2018; Teo, et.al., 2019). Hence, growing economy at expense of environmental quality and or huge infrastructural development impairment is abnormal.
According to (Chukwueyem et al., 2015; FGN, 2017; Sulaiman and Abdul-Rahim, 2018; Wang, Li and Fang, 2018), quest for better standards of living and increased population drive increase in human activities such as infrastructure development, natural resources exploration, industrialization, GHG emissions, pollution, climate change and food insecurity etc., with long-run impact on the economy. This is evident in the Nigeria’s population growth rate at about 3%, estimated 17million housing deficit, 66.9% land use change effects for urbanization, huge disruption to the ecosystem, social and economic costs that influence market failures (Maliszewska and Mensbrugghe, 2019). Figure 1 below compares economic growth proxy by GDP growth rate and CO2 emission in Nigeria, and underscores the common argument that environment impairment increases with increase in industrialization leading to economic growth, however, reversible with public regulatory policies.
Globally, regulatory policies have favored the concept of green economy across sectors (World Bank, 2019). These policies emphasizes sustainability concepts such as growing the economy yet improving environmental quality by exploring the routes of fight against climate change, environmental taxes, carbon pricing, renewable clean energy sources, innovative energy incentives etc.(Zelenˇáková, Fijko, Diaconu and Remenˇáková 2018). In Nigeria, green economy policies such as (Environmental Impact Assessment Act, (EIA) 1992, Sustainable Development Goal, 2015) indulge infrastructures planning stage nexus with the environmental quality and protection on certain class of economic infrastructures projects for which EIA report must be conducted and approved before implementation. Additionally, reducing negative effects of infrastructures development through effective preventive maintenance, motivation and innovation via alternative mode of transportation etc.
2.2. Theoretical review
Earlier thoughts on input- output assumption related to economic growth (Y’) have been severally considered and agreed as a production function by the classical (Smith, 1776) centered on rate of population growth or Labour (l) and particularly Land (d) and its resources use (agriculture, minerals etc.) as disruptions that influence growth simply expressed as;
Y’=f (l, d)……………………………….……………….……..1
The neoclassical growth (Solow; 1956) theorists further argued that the use of Land (d), Labour (l) inclusive of Capital (k) (e.g. financial resources) with influence of technological progress (A) will result in a long-run output growth in an economy, simply expressed thus;
Y’=f A(l, ,d k)……………………………….…………………..2
Here A shows productivity level of technical progress (like infrastructures development and machines) that facilitate efficiency of other factor inputs for improved output and hence growth (Babatunde, 2018) assuming constant return to scale, except on capital.
From the foregoing models, it shows that environmental factors are taking for granted and seldom accounted for in growth modelling while knowing that natural resources input factors are high demand but scares in supply processes since they exert environmental risks as negative externalities in the production process (Maliszewska and Mensbrugghe, 2019; Wolde, 2015). However, Environmental Kuznets Curve (EKC) is widely believed to explain the economic growth- environmental risk relationship emphasizing that as per capita income rise, pollution and other forms of environmental degradation would rise first and then fall in an inverted-U pattern. Further, critiques have emphasized that environmental risks nexus economic growth negatively (Cumming and Cramon-Taubadelb, 2018) especially in developed economies in modern growth theories. Therefore, environment impairment (e) assumes to increase with fixed capital (K)(infrastructures development) and in turn may increase/decrease economic growth;
Therefore modern growth modelling assumptions approach to input- output assumption related to economic growth (Y’), is appreciably inclusive thus;
Y’=f A(l, ,d k, e)……………………………….…………………..4
2.3 Empirical reviews
Shuaibu and Oyinlola (2013) established no causal link between CO2 emissions and energy consumption to economic growth due to structural shifts. Using time-series analysis on annual data from 1981 to 2013, and adopting residual-based cointegration test with a structural break, it was found that there is current account sustainability in Nigeria and structural changes were not very potent during the period under consideration. This implies that the Nigerian economy complied with the IBC hypothesis, suggesting that exports could actually finance imports. Sahrir , Bachok and Osman,(2014) studied Environmental and Health Impacts of Airport Infrastructure Upgrading: Kuala Lumpur International Airport and found that significant environmental concerns are noise and air quality. Using field survey, sampling and analyzing noise level and airborne particles of the outdoor and indoor at the Airport construction and adjacent sites thus, recommended increased construction site environmental sensitivity methodology and land use.
Chingoiro & Mbulawa, (2016) examined Economic growth and infrastructure expenditure in Kenya. Using annual data on GDP growth rate, infrastructure spending and labour for the period 1980 to 2013 and employed Granger-Causality approach, it was found that there is bidirectional flow of causality between economic growth and infrastructure, recommending that the government should commit more funds towards developing infrastructure in the short term. Alege, Adediran and Ogundipe, (2016) investigated Pollutant emissions, energy consumption and economic growth in Nigeria to find the direction of causal relationships among emissions, energy consumption and economic growth using annual time series data for the period 1970-2013 and adopting Johansen maximum likelihood cointegration and Granger causality tests. While the result showed existence of cointegrating vector between the variables at long run that is, fossil fuel enhances carbon emissions in the atmospheric, it also show existence of unidirectional causation from fossil fuel to CO2 emissions and GDP per capita.
Cumming and Cramon-Taubadelb, (2018) studied Linking economic growth pathways and environmental sustainability by understanding development as alternate social–ecological regime by analyzing thethe red loop– green loop (RL-GL) model that proposes growth defined by Human Development Index (HDI) is explained by social–ecological interactions shift proxied by populations growth, traditional cultural practices, natural resources per capita GDP. using Pearson’s correlation and found that environmental and ecological sustainability are increasingly significant in economic growth but with little effect in development practices. In Nigeria, (Mba, 2018) adopted primary and secondary sources in a study on Assessment of Environmental Impact of Deforestation in Enugu, Nigeria, and concluded that major contribution to deforestation in this area is urbanization and industrial development caused by population increase and recommended that government ensure public awareness, monitoring and enabling laws to deter the trend. Babatunde, (2018) investigated government spending on infrastructure and growth using primary and secondary data from 1980 to 2016 in Nigeria and adopted Weighted least square model and found that government spending on transport and communication, education and health infrastructure has significant effects on economic growth in Nigeria.
Li, et al. (2019) examined the environmental impact assessment of transportation infrastructure life cycle using the three phases of construction, maintenance and repair, and demolition of the fast track transportation project in China, by taking measurement of materials used and the energy consumed as environmental emissions, and found that construction, demolition and maintenance phases have environmental impact in descending order especially in the use of steel material. Sturup and Low (2019) examined Sustainable development and mega infrastructure: an overview of the issues in China and found that a strong relationship between global ecosystem and mega infrastructure development, asserting a balanced sustainability concepts for physical development of infrastructures. Odugbesan and Rjoub (2020) assessed the relationship Among Economic Growth, Energy Consumption, CO2 Emission, and Urbanization: Evidence From MINT (Mexico, Indonesia, Nigeria, and Turkey) countries employing the ARDL Bounds test approach, and the result revealed that the energy–growth hypothesis has unidirectional causality from energy consumption in Nigeria and Indonesia amongst others and show a long-run relationship with economic growth, energy consumption, and CO2 emissions. Urhie et al., (2020) examined economic growth and environmental impacts relationship by adopting moderated mediation model to assess the cyclical effects of these economic relationships of air pollution and health outcomes and found significant interaction between air pollution and government expenditure on health performance hence asserting that environmentally friendly production and consumption pattern minimize environmental hazards and recommended that preventive public policies to adverse health outcomes on manufacturing firms.
Some of the studies reviewed establish that infrastructures and or environmental concerns explain growth using different estimation techniques. However, none of the studies reviewed established infrastructures development, environment quality and economic growth nexus particularly as related to Nigeria, indicating paucity of studies in this area.