Author: Godswill Unekwuojo Musa

godswillumusa@gmail.com

image source: https://cutt.ly/qoEBbVg

INTRODUCTION
Sustainable Development has become a guiding paradigm to create a new kind of built environment. It has been defined as development that meets the needs of people without compromising the ability of future generations to meet their own needs (WCED, 1987). In urban planning, as in other professions, this has meant a new recognition of how environmental and social aspects of development need to be integrated with economic development, as well as meeting basic human needs for the poorest parts of the world. Sustainability is not an end goal, but a journey that local governments can take to improve the social equity, environmental, and economic conditions in their jurisdiction. A common framework to guide their efforts is a sustainability plan, which ties together a community’s goals, strategies, implementation plans, and metrics for improving sustainability.


The creation, operation and disposal of the built environment dominate humanity’s impact on the natural world (Kibert et al., 2000). It is obvious that the construction industry is the principal destroyer of the natural environment. It is a major consumer of non-renewable resources, produces large volume of waste, pollutes the air and water, and contributes to land dereliction. A primary goal of sustainability is to reduce humanity’s environmental or ecological footprint on the planet. Sustainable cities are environmentally safe, socially inclusive and economically productive. The goal 11 of the sustainable development goals (SDGs) emphasizes the need for sustainable cities and communities. Achieving this goal entails careful balancing of environmental management objectives against built (or human) environment objectives, as it is through the latter that basic human needs are met (UN-Habitat, 2009). Action to attain these objectives provides the link between the natural and the built environment, or between the green and brown agendas which is the focus of discussion in this paper.

THE GREEN AND BROWN AGENDAS
The green agenda is about the natural systems of the local, bioregional and global ecosystem, which are used by cities and other settlements as services for open space, biodiversity, water provision, waste dispersion, healthy air, and reliable climate, food and fiber. One of the aims of urban planning is to ensure that the green agenda is managed effectively, as green functions in a city are not always provided through the market mechanism. The changes that have been made to ecosystems have contributed to substantial net gains in human well-being and economic development. Since 1960, while the world’s population has doubled and economic activity increased sixfold, food production has increased 2.5 times, food prices have declined, water use doubled, wood harvest for pulp tripled, and hydropower doubled (UN-Habitat 2009). But these gains have been achieved at growing ecological costs which, unless addressed, will substantially diminish the benefits that future generations obtain from ecosystems.


The brown agenda is essential for making a city work, for a healthy and livable environment, and for creating the human and economic opportunities that have driven cities throughout their history. All cities including Nigerian Cities consume land and resources such as energy, water and materials, which they use for buildings and transport. In the process of making a city functional, these resources are turned into wastes. The brown functions of a city generally consume and degrade its green resources and processes, respectively, unless the city intervenes through processes such as urban planning and environmental management. Thus, the brown agenda is about the optimization of land use, engineering of waste systems, the minimizing of energy consumption and transport, the reduction in use of materials, and the creation of an efficient built environment. These systems have always been provided in cities using an increasing ecological footprint. In other words, the brown agenda has always tended to assume the green agenda, to consume it and to dominate it. Since this is no longer feasible, cities need to reduce their impact upon the natural environment locally, ensure that bioregional ecosystems are not degraded and that the global ecosystem is not damaged by climate change.


The goal of sustainable urban development is to reduce the impact of consumption of natural systems (global, regional and local) by the city thus keeping within natural limits, while simultaneously enabling human systems to be optimized for improving the quality of urban life (UN-Habitat 2009). A significant practical dilemma that faces planners as well as other urban professionals and politicians when they try to implement sustainable urban development is how to integrate the two different sets of concerns of the ‘green agenda’ and the ‘brown agenda’ (i.e. the natural environment and the human environment).

HOW THE GREEN AND BROWN AGENDAS CAN BE INTEGRATED FOR SUSTAINABLE DEVELOPMENT IN NIGERIA CITIES
Some major trends in the integration of the green and brown agendas in cities have been identified by UN-Habitat (2009) and can also be applied to Nigerian Cities.

i. Development of renewable energy
Nigerian Cities such as Lagos, Port Harcourt, Abuja, Kano among the rest are predominantly dependent on non-renewable sources of energy most especially burning of Hydrocarbons for generating electricity domestic and industrial use. These non-renewable source of energy contributes to environmental problems as burning of fossil fuels is a large contributor of atmospheric greenhouse gases such as carbon dioxide that eventually results to climate change that causes hazards such as global warming and flooding. Renewable energy such as solar energy, wind energy, hydro-power, geothermal energy and biofuels enables a city to reduce its ecological footprint.

Renewable energy production can and should occur within cities, integrated within their land use and built form, and comprising a significant and important element of the urban economy. Cities are not simply consumers of energy, but catalysts for more sustainable energy paths, and can increasingly become a part of the Earth’s solar cycle. Movement towards a renewable energy future will require much greater commitment from Nigerian Cities themselves at all levels, including at the local and the metropolitan levels.
Urban planning is necessary to create the infrastructure needed to support solar and wind power at the scale required to help power a city. There are significant opportunities to harness solar and wind power; like photovoltaic solar power can be integrated within Nigerian cities and their buildings. For example, Cape Town (South Africa) has an Integrated Metropolitan Environmental Policy, which has an energy strategy designed to put the city in the lead ‘in meeting energy needs in a sustainable way, where everyone has access to affordable and healthy energy services. This integration of the green and brown agendas includes 10 per cent of the energy supply coming from renewable sources by 2020. Another example is Adelaide, which has gone from 0 to 20 per cent renewable energy in ten years by building four large wind farms.
ii. Striving for carbon-neutral cities
Carbon-neutral cities are able to reduce their ecological footprint through energy efficiency and by replacing fossil fuels, thus providing a basis for ecological regeneration by creating offsets in the bioregion (UN-Habitat 2009). Carbon neutrality can become the goal for all urban development but will require: reducing energy use wherever possible; especially in the building and transportation sectors; Adding as much renewable energy as possible, while being careful that the production of the renewable energy is not contributing significantly to greenhouse gases; and Offsetting any CO2 emitted through purchasing carbon credits, particularly through tree planting.


iii. Distributed power and water systems
Decentralization of power and water supply systems aims to achieve a shift from large centralized power and water systems to small-scale and neighbourhood-based systems within cities, including expansion of the concept of green infrastructure. The distributed use of power and water can enable a Nigerian Cities to reduce its ecological footprint, as power and water can be more efficiently provided using the benefits of electronic control systems; particularly through water-sensitive urban design, a city can improve its green character. In large cities such as Lagos and Kano, the traditional engineering approach to providing energy has been through large centralized production facilities and extensive distribution systems that transport power relatively long distances.
The distributed water system approach is called ‘water sensitive urban design. It includes using the complete water cycle (i.e. using rain and local water sources such as groundwater to feed into the system and then to recycle ‘grey’ water locally and ‘black’ water regionally, thus ensuring that there are significant reductions in water used). Grey water recycling can similarly be used to irrigate green parks and gardens, and regional black water recycling can be tied into regional ecosystems. All of these initiatives require ‘smart’ control systems to fit them into a city grid and also require new skills among town planners and engineers, who are so far used to water management being a centralized function rather than being a local planning issue. Decentralized energy production systems offer a number of benefits, including energy savings, given the ability to better control power production, lessen vulnerability and achieve greater resilience in the face of natural and human-made disaster (including terrorist attacks).


iv. Increasing photosynthetic spaces as part of green infrastructure
The use of photosynthetic processes in cities reduces their ecological impact by replacing fossil fuels and can bring substantial ecological benefits through emphasis on natural systems. There has been a positive trend in planning in the direction of an expanded notion of urban infrastructure that includes the idea of ‘green infrastructure’ based on photosynthetic processes. Green infrastructure refers to the many green and ecological features and systems, from wetlands to urban forests, which provide a host of benefits to cities and urban residents clean water, storm water collection and management, climate moderation and cleansing of urban air, purposes without the distribution or transport losses so apparent in most cities today. A green roof for biodiversity purposes, water collection, photovoltaic collectors or biofuel algal collectors can possibly become a solar ordinance set by town planners as part of local government policy.

v. Increasing sense of place
An approach for creating local enterprises that builds on the passions and resources of the local community and supports local businesses in their early vulnerable steps is a method of creating a sense of place in Nigerian Cities. Pioneers of these initiatives have found, time and time again, that place really matters. When people have a sense of belonging and an identity in their town or city, they are keen to create local enterprises. When communities relate strongly to the local environment, the city’s heritage and its unique culture, they develop a strong social capital of networks and trust that forms the basis of a robust urban economy. As part of their local economic development priorities, many cities are placing increasing emphasis on local place identity, as social capital has been found to be one of the best ways to predict wealth in a community. Producing power from solar, wind or biomass in the locality or region is very much an economic development strategy that can generate local jobs and economic revenue from land (farmland) that might other- wise be economically marginal, in the process recirculating money, with an important economic multiplier effect. Energy efficiency can also be an economic development strategy.


vi. Sustainable transport
The state of Transportation in Nigerian Cities, neighborhoods and regions are really in a state of unsustainability and has been faced with so many challenges such as congestion, overcrowding, pollution, greenhouse gasses emission, accidents and so on. Sustainable transportation should be adopted increasingly being designed to use energy sparingly by offering walkable transit-oriented options, often supplemented by vehicles powered by renewable energy. Cities with more sustainable transport systems have been able to reduce their ecological footprints from their reduced use of fossil fuels, as well as through reduced urban sprawl and reduced dependence upon car- based infrastructure. Very high-density city centres mean that most destinations can be reached with a short walk or they can have highly effective public transport opportunities due to the concentration of people near stations. If densities are generally lower, but higher along corridors, it is still feasible to have a good transit system. If, however, low densities are the dominant feature of a city, then most activity needs to be based around cars as they alone can enable people to reach their destinations in a reasonable time.

vii. Developing cities without slums
Slums usually have dire consequences for the urban environment. They often deprive the city of foreshore land for flood control and natural bio-filtration from fringing wetland vegetation; severe erosion can result from steep slopes when they are settled upon; and, as the only source of domestic energy for slum dwellers is firewood, nearby land on the periphery of the city is often deforested. Thus slums pose a significant threat to the green agenda. At the same time, the brown agenda for those living in the slums is seriously compromised as well. Most slums in developing country cities are generally built on empty public or private land on the periphery of the city, or elsewhere on physically unsafe land that is vulnerable to natural hazards. Often, such land is on steep slopes prone to landslides or in low-lying areas prone to flooding, or is so severely contaminated that no one else in the city wants it. In Nigerian cities, Slums develop because of a combination of rapid rural urban migration, increasing urban poverty and inequality, marginalization of poor neighbourhoods, inability of the urban poor to access affordable land for housing, insufficient investment in new low-income housing, and poor maintenance of the existing housing stock.
Most slum housing is built of simple and often makeshift materials that can only provide rudimentary protection against natural hazards. Invariably, levels of access to clean drinking water and safe sanitation are extremely low, resulting in basic health problems. The United Nations Global Report on Human Settlements in 2003 entitled The Challenge of Slums presented the first global assessment of slums, emphasizing their problems and prospects. It showed that in many developing country cities including Nigerian cities, the numbers of slum dwellers far exceeded the numbers in formal residences. At present, slum dwellers constitute 36.5 per cent of the urban population in developing countries, with the percentage being as high as 62 in sub-Saharan Africa and 43 in Southern Asia. The question of slums only in terms of the integration of the green and brown agendas and how this is contributing towards the realization of the goal of cities without slums is a major issue.


CONCLUSION
The concept of sustainable development in cities has challenged urban planning to find new ways of addressing the pressing issues of urban poverty and wealth creation while simultaneously addressing urban environmental issues, both natural and built, and the social and cultural issues of urban communities. In integrating Green and Brown Agendas within Nigerian Cities: material waste generated during construction is reduced or recycled; Energy efficiency is improved, perhaps by relying on the use of natural light and ventilation or solar power; Less water is used, or rainwater harvesting system is installed to ensure wiser use; Measures taken to make buildings and construction more sustainable rely increasingly on life cycle approaches; Working with the community to enable them to participate in the development process and in the management of infrastructure can enable a slum community to thrive and develop pride in their green and brown achievements; They can become models of sustainability as they Slums pose a significant threat to the green agenda; and slum upgrading which is largely concerned with the brown agenda create reduced levels of resource consumption while creating healthy and attractive living environments for the residents.

REFERENCES
Kibert, C., Sendzimir, J., and Guy, G. B. (Eds.). (2000). Defining an Ecology of Construction. Construction Ecology: Nature as the Basis for Green Buildings. New York: Spon Press, 7-28.
Nwokoro I. (2011). Sustainable or Green Construction in Lagos, Nigeria: Principles, Attributes and Framework: Department of Urban and Regional Planning, University of Lagos, Lagos, Nigeria
Robert W. Kates, Thomas M. Parris, and Anthony A. Leiserowitz (2005). What Is Sustainable Development? Goals, Indicators, Values, and Practice: London UK.
UN-Habitat (2009). Planning Sustainable Cities Global Report on Human Settlements: United Nations Human Settlements Programme: Nairobi, Kenya.
WCED (1987). Our Common Future; The Brundtland Report, Oxford: Oxford University Press.