1 Introduction
Besides rapid urban population growth and urban land expansion, cities in Africa are characterised by high levels of informality and poverty, poor infrastructure, and consequently a high susceptibility to environmental hazards. Climate change and its impacts are exacerbating the environmental pressures on cities. Hence, climate-resilient conditions must emerge as principles for the sustainable development of cities.1
In an array of options to improve the overall resilience of cities, the importance of urban green spaces (ugs) is widely recognised. Urban green spaces strengthen a city’s ability to cope with and recover from stress. However, both urbanisation and changing climatic conditions threaten the existence of green spaces in cities. Despite this, their continued existence can be ensured through specific management and planning efforts that lead to urban vegetation being adequately integrated into the city matrix, thereby also sustainably supporting urban climate resilience. These strategies include ecosystem services that aim to reduce the impact of floods and heatwaves, improve air quality, and contribute to food security.
Although increasing global urbanisation and its environmental, economic, and social problems have been intensively discussed, approaches to enhancing urban climate resilience in developing countries demand further scientific investigation. As such, this chapter (1) elaborates on urbanisation in Africa, (2) discusses urban land expansion and environmental challenges in the context of climate change, and (3) examines the potential of ugs to contribute to urban climate resilience and addresses managerial challenges hindering ugs conservation in Kumasi (Ghana), a mid-sized sub-Saharan African city.
Urban resilience refers to the ability of an urban system and all its constituent socio-ecological and socio-technical networks across temporal and spatial scales to maintain or rapidly return to desired functions in the face of a disturbance, to adapt to change, and to quickly transform systems that limit current or future adaptive capacity.3
Climate resilience in natural and human systems depends strongly on their ability to adapt to climate change (equilibrist resilience) as well as to mitigate the effects of climate change (evolutionary resilience).4 In this context, adaptation refers to reactive adjustments in response to actual or expected climatic stimuli and their effects or impacts, whereas mitigation comprises proactive anthropogenic interventions to reduce the sources or enhance the sinks of greenhouse gases (ghgs).5 Ultimately, both approaches aim to minimise the undesirable effects of climate change6 and, accordingly, play a crucial role in urban climate resilience.
2 Urbanisation in Africa
About 54 per cent of the world’s population now lives in urban areas, and it is projected that many more people will move to cities in the coming decades. At the turn of the 20th century, Africa contributed less than two per cent of the world’s urban population, a figure that has now reached twelve per cent. The continent’s urban population has soared from ten per cent of its total population in the 1950s to forty per cent (439 million) today and is projected to reach 56 per cent (1.1 billion) by 2050. The number of African megacities is expected to double by 2030, while that of medium-sized cities will quadruple.7 Africa will become the most rapidly urbanising continent between 2020 and 2050, while by 20508 its cities are expected to account for 21 per cent of the world’s urban population.
2.1 Historical Background
As early as 3200 bc, large settlements already existed in Africa, initially confined to North Africa before later emerging in sub-Saharan Africa (ssa) too.9 Ancient urban centres and peri-urban areas were characterised by their ability to produce agricultural surpluses, specialised craftsmen, and monumental architecture.10 Compared to contemporary urban centres, however, cities in ancient Africa were sparse, low in population, and small in size, although vibrant politically, economically, and socially.
Contact with Arab and later European merchants and missionaries fostered the rapid spread and development of cities.11 Colonisation, economic expansion, and international politics changed the face of African cities for both colonialists and indigenes. Cities, especially those along the coasts of the Indian and Atlantic oceans, were renowned for their trade in slaves and natural resources from the African continent. To facilitate trade, contemporary European and Arabian architecture, technology, and culture were gradually infused into African cities and culture. Indeed, the history, shape, and character of most African cities today can be traced to colonial city plans, designs, policies, and functions.12 For instance, urban plans for Lusaka (Zambia) and Kumasi were based on Howard’s ‘Garden City’ concept—the archetypical car-oriented, elitist European city. Colonial master plans, however, did not anticipate the sprawl that has redefined the shape and configuration of modern African cities.13
2.2 Current Situation and Trends
Cairo (Egypt), Kinshasa (DR Congo), and Lagos (Nigeria) are the only megacities (ten million inhabitants or more) on the African continent, together contributing 15 per cent of its total urban population. About 66 per cent of Africa’s urban population lives in medium-sized cities with one to five million residents. Of these, 16 cities are in West Africa (e.g. Abidjan, Accra, Dakar, Kano), nine in Southern Africa (e.g. Harare, Johannesburg, Lusaka, Maputo), seven each in North Africa (e.g. Algiers, Fez, Rabat, Tripoli) and East Africa (e.g. Addis Ababa, Mogadishu, Dar es Salaam, Nairobi), and four in Central Africa (Brazzaville, Douala, Mbuji-Mayi, and Yaoundé). Small cities (fewer than one million inhabitants) are generally regarded as the fastest-growing cities in the world (2.4–6 per cent per year).14
Although Africa remains the least urbanised continent, subregional variations are significant. Excluding Mozambique, Zambia, and Zimbabwe, Southern Africa is the most urbanised subregion with 61 per cent of its population living in urban areas, followed by North Africa with 51 per cent. In Central and West Africa, the urban share is about 44 per cent, higher than in East Africa, where it is 25 per cent. Most African urban populations are concentrated in coastal areas (e.g. Gulf of Guinea), alluvial plains (e.g. Nile River), or lacustrine plains (e.g. Lake Victoria).
Urbanisation is most rapid in East and West Africa, where by 2050 the urban population will rise to about 328 million and 390 million respectively (Figure 11.1).15
Urban population growth in the African subregions
2.3 Causes: Migration and Natural Increase
Recent urbanisation in Africa has been attributed to demand for labour during the continent’s early period of industrialisation from the late 19th century until the middle of the 20th century, which triggered the exodus of rural people into towns and cities.16 Additionally, civil unrest and violence due to political instability, natural disasters provoked by climatic events (such as drought- or flood-induced famine), alienation of individuals from tribes and indigenous communities, and simply the desire to experience urban life have all been causal factors.17
Natural population increases through high birth rates and/or the reclassification of former rural areas as urban now provide the most striking explanations for current urbanisation patterns in Africa.18 The availability of better healthcare systems in cities has increased natality while reducing mortality rates. In resource-rich countries like Ghana, Côte d’Ivoire, or Nigeria, proceeds from the export of natural resources are disproportionately invested in developing urban goods and services, in turn further accelerating urbanisation.19
However, due to a lack of opportunities in cities, high living costs, and cultural discomfort experienced by migrants, rural–urban migration is decreasing.20 In Burkina Faso and Côte d’Ivoire, for example, counter-urbanisation processes have been observed. Nevertheless, inter- and intra-city mobility among urbanites remain widespread.21 The pressing question now becomes how urbanisation in Africa will influence urban life economically, socially, culturally, and environmentally.
2.4 Side Effects of Urbanisation: Poverty and Cultural Erosion
Between 1981 and 2004, the number of urban poor (income below usd 2.15/day) was rising even faster than the global urban population.22 By 2050, forty per cent of the 1.1 billion African urbanites will live in income poverty, representing the largest and fastest-growing group of impoverished people in the world.23 As a consequence, Africa’s urbanisation is characterised by an inadequate asset base (such as lack of infrastructure), unavailability of and uneven access to services, amenities, education, and human capital development, as well as worsening environmental conditions.24 Thus, African cities are not always the engines of economic growth that cities on other continents typically are; instead, they are often both a cause and symptom of various crises.25 Although these trends are changing—with many African cities now acting as hubs of innovation—the pace of change is slow, and most of the continent remains marked by a scarcity of development opportunities and a high proportion of unskilled labour. Most cities, meanwhile, are primarily centres of administrative and political power that remain short of skilled manpower.
Although research on a continental scale is lacking, country-level studies indicate that the majority of Africa’s urban poor live in East, Central, and West Africa.26 For example, thirty per cent of the population in Mombasa (Kenya) live below the absolute poverty line (usd 2.15/day),27 fifty per cent of the population of Maputo (Mozambique) is poor and thirty per cent characterised as destitute,28 while 95 per cent of informal economy participants in Kinshasa (DR Congo) have low incomes while ninety per cent have no formal jobs.29
Cities also perform the role of hubs of foreign culture and technology that influence local ones. For instance, the large extended family system and communal way of life are giving way to a nuclear family system, individualism, and a struggle for survival as conflict increases in poor urban neighbourhoods. One such example is Mombasa, where frequent clashes occur between coastal residents and up-country immigrants due to economic inequality fueled by a political system that is ethnically inclined.30 Technology and mechanisation have replaced manual and animal traction. Organic waste, formerly an important resource as fertiliser, has become adulterated with non-biodegradable materials and is thus a menace to public health in cities. In many African cities, waste is improperly disposed of. Waste and landfills pollute soil, air, and water, produce foul smells, provide breeding grounds for disease vectors, and attract dangerous animals such as rodents and snakes.
3 Environmental Impacts: Land Use and Climate Change
3.1 Urban Land Expansion and Land Use Change
Globally, urban areas occupy about three to four per cent of the earth’s surface and are growing at a rate twice that of the global population.31 With 256 cities (more than 100,000 inhabitants each) and a total population of 131.6 million, urban areas in ssa occupy an area of approximately 13,000 square kilometres, while 115 cities in North Africa with a population of 53 million occupy an area of 5,342 square kilometres. Together, all these urban areas are predicted to increase in space by 590 per cent by 2030.
Urban expansion occurs unevenly across the continent, mostly concentrated in the Gulf of Guinea region of West Africa, along the Nile River in Egypt, on the northern shore of Lake Victoria in Kenya and Uganda and stretching into Burundi and Rwanda, in the Kano region in northern Nigeria, and in greater Addis Ababa in Ethiopia.32 Losses in natural land cover to urbanisation are higher in East, North, and West Africa than in Southern and Central Africa.33
Generally, megacities and medium-sized cities are undergoing the most rapid land expansion with significantly higher growth rates of 743 and 620 hectares per year respectively (Table 11.1).34 However, small cities with fewer than one million inhabitants are numerous and therefore growing rapidly in terms of their share of the total population, with an average land expansion rate of 129 hectares per year.
Expanding cities encroach upon environmentally sensitive zones such as wetlands, protected nature areas, agricultural land, and open parkland, causing a decline in vegetation cover and primary production.35 Cities in ssa have historically experienced a growth in built-up areas at the expense of agricultural and forest land, causing 12 to 77 per cent loss in tree cover and 18 to 50 per cent loss in farmland within an average period of 22 years.36 However, this trend is not universal; in Bamako (Mali), non-forest green spaces increased between 1986 and 2006 due to bare land conversion.37
Changes in urban land use characteristics in mega, medium-sized, and small cities in Africa (average values)
| Citytype | City area (km2) | Period of change (years) | Increase in built-up area (km2) Percentage change (%) | Decrease in green space (km2) Percentage change (%) | Urban expansion rate (ha/year) | Green space coverage (%) | Green space per 1,000 inhabitants (ha) |
| Mega | 972 | 23 | 170 (93%) | 165 (46%) | 743 | 42 | 0.47 |
| Medium-sized | 844 | 21 | 135 (199%) | 120 (22%) | 620 | 39 | 12.1 |
| Small | 214 | 24 | 22 (148%) | 22 (21%) | 129 | 57 | 23 |
While many underlying factors influence urban land expansion, in Africa this is primarily driven by population growth, evidence for which is demonstrated by the correlation between population growth and increase in urban land area across the continent.38
Vegetation loss due to urban land expansion exacerbates climate change impacts. By replacing trees with grey infrastructure, the carbon stored in vegetation and soil is released into the atmosphere via several processes. At an average urban built-up area expansion rate of five hundred hectares per annum (Table 11.1), ssa cities emit about 100,000 tons of carbon per year due to urbanisation-driven forest loss. It is estimated that urban expansion-related deforestation in Africa will emit approximately 490 million tons of carbon by 2030. However, urbanisation-driven vegetation loss and its effects on greenhouse gas (ghg) emissions and climate change require further investigation at higher resolution given the wide ecological and socio-economic disparities among African cities. Furthermore, land use change may have much more drastic thermal effects in urban areas than climate change. A simulation study on land surface temperature in Addis Ababa (Ethiopia) and Dar es Salaam (Tanzania) revealed converting vegetation to a built-up or bare area may result in a land surface temperature difference of up to 25°C compared to typical climate change-related increases of about 1.5°C requiring several decades to occur.39 Also, the sealing of soil surfaces in cities redefines water flow paths, impedes infiltration, and facilitates overland flow, thereby causing more frequent flash floods and major flood events.
However, urbanisation does not necessarily exacerbate loss of vegetation. In arid areas, the environmental conditions in cities can actually provide favourable conditions for plant growth and hence induce city greening due to elevated CO2 emissions, soil nutrient improvements from wastewater irrigation and organic waste disposal, and higher temperatures.40
Sixty per cent of households in African cities use fuelwood for cooking.41 Fuelwood, together with charcoal, is also the predominant source of energy in African cities, particularly for the poor, and thus a notable contributor of CO2 emissions.42 Fuelwood usually comes from forests in peri-urban and neighbouring hinterlands. In the Dar es Salaam area, the radius of exploitation areas for fuelwood and charcoal in the surrounding forests expanded at rates of nine and two kilometres per year respectively, with a reduction in carbon storage and species richness experienced within a radius of up to 220 kilometres from the city centre.43 Urbanisation in Africa is therefore expected to further exacerbate deforestation in hinterland areas and weaken the potential for terrestrial carbon sequestration, consequently affecting temperature, relative humidity, and precipitation patterns in the respective urban areas.
3.2 Impacts on Quality of Life and Health
Human activities lead to an increase in urban temperature, a phenomenon known as the urban heat island (uhi) effect. This refers to the difference in temperature between urban and suburban or rural areas44 and is attributable to several factors. These include the physical properties of urban land cover, such as dark and compact surfaces (with their absorption of solar radiation, low albedo, and high heat capacity), the increase in high-rise buildings with multiple sunlight-reflecting and -absorbing surfaces as well as wind-blocking effects (caused by their canyon-like heat-trapping structures), and the decrease in area covered by vegetation (resulting in a decline in evaporative cooling).45 A recent evaluation of uhi effects in cities worldwide, including 47 in Africa, revealed differences in day- and night-time temperatures between urban and suburban areas of 1.5°C and 1.1°C respectively. Moreover, the effects of rising air pollutant concentrations in cities interact with uhi, exacerbating health burdens on cities.46
Other climate-related vulnerabilities include the prevalence of waterborne diseases such as cholera, malaria, dengue, and yellow fever,47 aggravated by floods and drought.48 In relation to the latter, over ninety per cent of the victims of precipitation-related disasters are comprised by the poor in informal settlements and slums.49
3.3 Urban Climate Resilience: Adaptation to and Mitigation of Climate Change
By taking into account their impressive concentrations of human capital, cities can, on the one hand, contribute to climate change or, alternatively, adapt to or also mitigate the effects of changing climatic conditions.50 Together, adaptation and mitigation strategies strengthen urban resilience to climate change and its impacts. Adaptive aspects of climate change resilience in cities include modification of the built environment and lifelines, promotion of urban green infrastructure, preventative action to reduce social vulnerability, fostering of climate change governance, and strengthening of strategic urban planning as well as the conducting of regular risk assessments while making such information available to decision makers and urbanites.51 Major efforts to promote urban climate change resilience in Africa have so far focused on strengthening the infrastructure base of local income communities, enacting policy reforms, engaging in reactive solutions like drainage construction after flood events, initiating poverty reduction programmes, and learning from the experiences of other cities. For instance, in Dakar (Senegal), which is prone to the coastal inundation and erosion that affects many other coastal cities in Africa, 3,000 reinforced housing units were constructed in 2005 for the relocation of flood victims, retention ponds were constructed in the floodplains, and floodplain settlement was prohibited.52 Experience from Kampala (Uganda) indicates that effective climate change adaptation requires community-based, infrastructural, and institutional interventions.53 However, in many African cities, the lack of capacity, know-how, and resource availability within national and local government stifles the effective implementation of climate resilience measures.54
Although climate change adaptation measures must be given highest priority, urban areas also have the potential to contribute to climate change mitigation. Mitigative strategies to reduce ghg emissions include, most importantly, promoting public transport systems, using renewable sources of energy, implementing improved waste management concepts, and maintaining or expanding ugs.55
Clearly, these adaptation and mitigation measures reflect the engineering, planning, and social policy ramifications of urban living, but their effectiveness is yet to be empirically substantiated. Conversely, there is now ample evidence that cities that were once considered mere sources of atmospheric carbon dioxide (CO2) can also take measures to act as carbon sinks. Estimates from cities in Europe and North America highlight the storage of considerable carbon stocks in ugs. In Leicester (United Kingdom), a city with an area of 73 square kilometres, aboveground vegetation stores about 231,000 tons of carbon dioxide. In the usa (where urban areas represent three per cent of the total land area), carbon storage in urban trees is estimated at 630–700 million tons. In Africa, ugs provide a feasible—albeit often neglected—alternative means of combatting the local consequences of climate change.
4 Case Study: Urban Green Spaces and Climate Resilience in Kumasi
4.1 Background
Kumasi is the second largest and fastest-growing city in Ghana, with a land area of 254 square kilometres and approximately 2.5 million inhabitants. The population density stands at about 8,000 inhabitants per square kilometre, while the annual population growth rate is 4.8 per cent.56 Not only is Kumasi a central point for transiting travellers from within and beyond the borders of the country, the city also plays host to the largest open market in West Africa, making it an important economic hub.57
In the early 19th century, urban Kumasi had a population of about 1,500 inhabitants concentrated on a land area of approximately two square kilometres.58 Its growth and development took place after the Asante Kingdom was defeated in the late 19th century by the British, who subsequently established Western infrastructure in the town. The construction of a railway opened up Kumasi to merchants from the coastal belt, while brisk trade, a cocoa boom, and the building of offices fostered new and refined infrastructural development beyond the town’s erstwhile boundaries. By 1950, Kumasi’s land area had expanded to 25 square kilometres. The city has since swelled to its present 254 square kilometres (Figure 11.2) and a population size of approximately 2.5 million residents.
Distribution of green spaces in Kumasi, Ghana
Once dubbed the ‘Garden City’ of West Africa because of its lush vegetation cover (which comprised ninety per cent of its total land area prior to the 1980s), Kumasi’s green cover has since decreased over time to about fifty per cent.59 The remaining green space is classified into eight dominant ugs types: natural forest, small plantations, farmland along streams, grassland, trees in institutional compounds, public parks, vegetation in cemeteries and sacred groves, and domestic gardens (Figure 11.2).
The changing climatic conditions in the city are quite apparent, with an increase of at least 1°C in daily minimum and maximum temperatures between 1970 and 200060 and a twenty per cent decline in precipitation over the past four to five decades having been reported.61 An increase in ghg emissions from the city’s transport sector from 665,000 to 860,000 tons between 2000 and 2005 was also reported, a rate of 39,000 tons per year with further implications for local climate.62
Biomass energy supplies 64 per cent of the total energy consumed in Ghana, with wood biomass consumption having increased by 72 per cent from 2004 to 2008.63 Together, Kumasi and Accra consume roughly sixty per cent of the total charcoal produced in Ghana. About 83 per cent of the energy consumed in low-income neighbourhoods in urban Ghana is from biomass.64 Considering the large piles of organic waste generated and its extensive fuelwood consumption, as reflected by the high proportion of its population engaged in charcoal and firewood collection for cooking, Kumasi has relatively high potential ghg emissions compared to other cities in the region.
Maintaining and managing ugs in Kumasi could offset some of its ghg emissions, minimise the effects of uhi, and help to improve the urban microclimate.
4.2 Urban Green Spaces: Contributions to Coping with Climatic Impacts in Kumasi
Green spaces contribute to urban climate resilience in diverse ways. Kumasi’s green cover is currently at about fifty per cent of its total land area and is believed to be contributing directly to the reduction of uhi. In cities such as Addis Ababa, Dar es Salaam, and Ouagadougou (Burkina Faso), areas with higher vegetation cover have been shown to be cooler.65 Evidence for the effectiveness of vegetation cover in combating uhi has also been recorded in Manchester (United Kingdom), where it was shown that by increasing vegetation cover by ten per cent, mean summer ambient temperatures decline by 3–4°C, reducing the amount of energy used for air conditioning and thus contributing to a decrease in energy demand for fossil fuels.66 Most residents in Kumasi use trees in green spaces such as domestic gardens and institutional compounds for shade (Figure 11.3) in order to cope with extreme heat during the day throughout the hot and sunny dry season. Shade under trees provides a cool place to relax, to do business, and for children to play. Additionally, the presence of green cover contributes to the cooling of homes through evapotranspiration, increases space between buildings, and alters the albedo of the urban landscape. This saves costs and cuts emissions due to a reduction in energy expended on air conditioning in offices and in some homes.
People in Kumasi under a Terminalia catappa tree (coping with heat)
Source: bertrand nero (author)
As well as acting as carbon sinks, green spaces also trap air pollutants (PM, NOx, CO, and short-lived pollutants e.g. CH4, O3, and hydrofluorocarbons) believed to be implicated in urban/global warming.67 On average, fifty to eighty per cent of fine particle (PM2.5) mass in Ghanaian cities is the result of biomass combustion, road dust, and vehicle emissions and, together with other air pollutants, causes up to 6,500 deaths countrywide annually. Low-income communities are more vulnerable than wealthier neighbourhoods. It is noteworthy that the magnitude of the overall effects of such particles on climate remains highly uncertain.68 Nevertheless, green spaces act as carpets preventing particles from being dislodged from bare surfaces, while trees trap and filter particles circulating in the air. Several studies have shown that urban neighbourhoods with adequate vegetation cover tend to have lower air pollutant concentrations indoors and lower rates of health burdens overall.69 In Kumasi, sixty per cent of green cover is composed of trees. This large amount of tree (green) cover has a significant air particle absorption and filtering capacity that leads to improved air quality and lowered risks of urban climate-related challenges.
Flooding is another urban climate challenge, for which residents of Kumasi have adopted various coping measures, including building embankments around houses, erecting buildings on stilts, using raised walkways, constructing drainage systems, and relocating to upland areas.70 However, like in most African cities, institutional (national and local government) capacities and resources to cope with climatic hazards are limited.71 A relatively simple approach such as appropriate integration of ugs into urban planning and incorporating necessary engineering measures could boost the flood-coping capacities of both local government and individual residents. Urban landscapes with fifty to ninety per cent impervious cover can yield as much as forty to eighty per cent surface run-off from incoming rainfall, whereas a forest landscape yields only 13 per cent surface run-off from similar precipitation events.72 Impervious surfaces decelerate infiltration rates and hence increase the likelihood of floods. Kumasi is traversed by several streams and wetlands and has about fifty to seventy per cent bare (built and non-built) land cover. Protecting and creating more wetlands, or where necessary dams, for flood mitigation, prohibiting human habitation and environmentally malignant activities near streams and wetlands (Figure 11.4), creating green spaces on non-built bare areas, and designating flood-prone regions and lowlands as green spaces for conservation should fundamentally enhance coping capacity for floods and boost urban resilience to climate change. Economic gains could also arise through the use of green wetlands for tourism and urban agriculture.
Building too close to the watercourse at Atonsu, Kumasi, Ghana
Source: bertrand nero (author)
4.3 Carbon Sequestration, Culture, and Urban Resilience in Kumasi
The functions of ugs described above involve reacting to urban climate hazards and thus conform to the stable, preservative view of equilibrist resilience.73 In this light, the city’s systems, agents, and institutions merely strive to cope with an adverse urban environment through, among other measures, the promotion of green spaces. However, ugs may assume a proactive, flexible, and transformative dimension geared at aiding the city to recover from shocks and establishing a new normality over the long term in line with the principles of evolutionary resilience.
In Kumasi as in other cities, active carbon sequestration in urban vegetation and soils, although relatively small in total amount, aligns well with efforts to keep the rise in global mean temperature to below 2°C relative to preindustrial times and thereby achieve lower urban temperatures as well as combat climate change.
It is estimated that the existing ugs cover in Kumasi stores up to 1,934,000 tons of carbon in aboveground trees, equivalent to 211 tons of carbon per hectare. This is similar to the regional average of 202 tons of carbon per hectare for African tropical forests.74 Remnants of natural forest as well as trees in public parks, and cemeteries have the highest mean carbon stocks, which are significantly higher than those of trees found on grassland, in domestic gardens, or on farmland. Differences due to species composition, stocking density, tree size, and age explain why ugs differ in their respective carbon storage capacities.75 Native tree species with high wood specific gravities and a diameter greater than one hundred centimetres dominate natural forest as well as vegetation in public parks, cemeteries, and to a lesser extent institutional compounds. Similarly, plantations and domestic gardens are characterised by small-sized trees of varied species, origins, and uses. Low carbon storage in grasslands is attributable to low tree density in such areas.
The benefits of ugs in relation to the offsetting of CO2 emissions are threefold:
- (1)the CO2 sequestered;
- (2)the emissions avoided due to shade and evaporative cooling, and
- (3)the emissions avoided due to climate regulation.76
In Kumasi, the CO2 equivalent (CO2e) of carbon storage in trees is currently estimated to be 7.1 million tons. Assuming that it takes fifty years to build up this level of carbon storage, the city’s average annual sequestration rate would be 142,000 tons CO2e. A rough estimate of CO2e emissions reveals that 500,000 tons CO2e are emitted in the city per year, including emissions from residential and non-residential areas, the transport system,77 and waste deposits.78 Accordingly, the share of CO2e sequestered annually by urban tree vegetation represents 25 to 30 per cent of Kumasi’s total emissions.
The benefits of tree carbon sequestration in Kumasi in terms of its monetary or CO2e value were estimated based on the social cost of carbon for 2010 using the procedures outlined in Nowak et al. The social cost of aboveground tree carbon storage was estimated to be usd 106.8 million for the city. This represents the amount of damage avoided by removing CO2 from the atmosphere and storing it in the city’s aboveground vegetation. This avoided damage further strengthens urban resilience to climate change.
Finally, ugs provide social and cultural benefits and may thus strengthen local communities in Kumasi. Trees in cemeteries, especially those emerging directly from gravesites, are believed to symbolise that the departed are now contently resting in heaven. Certain trees christened designated as ‘spirits’ and those around shrines (although few in number) may be preserved as a mark of respect for the relevant deity. Home gardening in urban areas can in some cases be interpreted as residents seeking to preserve their tradition of cultivation.79 To some, trees are symbolic representations of people, depicting parental care through the shelter they provide and their communal life when growing together in a forest.80 As meeting places for community members, ugs foster harmony and provide a platform for greater interaction where community challenges may be discussed. Therefore, ugs contribute in ways that go beyond making communities more resilient to environmental risks and change.
4.4 Managerial Issues: Stakeholders’ Interplay and Urban Green Spaces
Community participation is fundamental to the establishment of ugs, while a general consensus is crucial to make them effective. In developed countries, top-down mechanisms by which governments and local authorities plan, decide, and invest in promoting urban greening can be a seemingly hegemonic process, whereas in developing countries actions are determined more by bottom-up processes. Hence, policy instruments that are able to ensure social and environmental performance are key.
Managerial actions/decisions, actors, and underlying reasons that favour and weaken ugs existence and maintenance in Kumasi, Ghana
| Urban green spaces (ugs) | Favouring ugs | Weakening ugs |
|---|---|---|
| Plantation | What? Planting trees | What? Tree felling, tree cutting |
| Who? Private landowners, administrators of public institutions, chiefs | Who? Fuelwood gatherers, land developers, chiefs, city authorities (Kumasi metropolitan assembly), town and country planners | |
| Why? Aesthetics, shade, firewood, enhance social interaction, mitigate climate change, regulate biogeochemical cycles, carbon sinks | Why? Impediments to ‘development’, expansion in urban land, damage to public infrastructure (building foundations, electricity/telephone cables), public health and safety (habitats for dangerous animals, criminal hideouts), need for fuelwood | |
| Home garden | What? Food/fruit crop cultivation, lawns | What? Housing without home gardens |
| Who? Private residential heads, tenants in governmental residential areas | Who? Owner | |
| Why? Food security, augment household income, medicines, beautification, pleasure, improved air quality, inherited practice, shade, love of vegetation, provision of environmental services | Why? Fear of hazards like snakes, invasion by criminals or intruders; destruction of buildings/walls through roots and branches, cultural reasons, urbanisation (converting gardens into more profitable structures) | |
| Institutional compounds | What? Tree plantings | What? Bare compounds, land use change |
| Who? Heads/activists in institutions/public offices | Who? Institutional authorities/heads | |
| Why? Shade, fruits, beautification, windbreaks, erosion checks, boundaries, influence of management interest and background | Why? Public hazard, destroys buildings, habitats for dangerous animals, hideouts for criminals, fallen branches, generates waste, litter; lack of management know-how and tools, allocation to other uses e.g. building construction | |
| Farmlands | What? Cultivation of marginal lands | What? Uncultivated fields, use of black waters |
| Who? Tenant farmers, (unskilled) urban dwellers, labourers | Who? City authorities, land owners | |
| Why? Food production, income generation, pleasure | Why? High demand for land, urbanisation (land use change), flood prone, pollution source (fertilisers & pesticides) | |
| Cemeteries/sacred grooves | What? Tree cultivation, tree maintenance | What? Bare cemeteries, logging |
| Who? Traditional heads (chiefs), local/city authorities | Who? Traditional heads (chiefs), local/city authorities, tree thieves | |
| Why? Revere the dead, respect, traditional/cultural beliefs, fear of spirits beautification, shade | Why? Create space for more burial grounds, clear encroachment, demand for land | |
| Street trees | What? Plan(t) rows of trees along streets | What? Bare streets, logging trees, poor or no maintenance |
| Who? City authorities, local stakeholders, individuals | Who? City authorities (government), individuals | |
| Why? Beautification, provide shade and cool areas (private use also), improve visibility and reduce accidents | Why? Interfere with electricity cables, smooth roadways, reduce hazards e.g. falling branches, protruding stems, etc., change of land use e.g. into shops | |
| Public parks/gardens | What? Plant trees and grasses | What? Land use change |
| Who? Government, city authorities, investors | Who? City authorities, investors | |
| Why? Shade, recreation, entertainment, public health, beautification, tourism, conservation of genetic resources | Why? Poor foresight, high maintenance costs, more profitable alternative use (business opportunities), neglect | |
| Grasslands | What? Marginal lands | What? Conversion of grasslands |
| Who? Private land owners, city authorities (Kumasi metropolitan assembly) | Who? Private owners, city authorities | |
| Why? Flood mitigation, grazing, biodiversity conservation | Why? More profitable alternative use, better alternative land uses, urbanisation (pressure for land use change) |
In this context, the resilience premise was applied to identify factors that favour or negatively influence the existence and maintenance of ugs.81 This implies that increasing urban resilience to climate change requires improving populations’ adaptation and mitigation capabilities as described above. Resilience may include societal and ecological subsystems in mutual interaction82 and is circumstance- and time-dependent, relying on constant adjustments within the system in response to external changes, thus leading to adaptive processes.83
The performance of each ugs and its potential to contribute to urban resilience to changing climatic conditions were assessed against the following contrasting criteria:
- (1)the strengthening decisions and actions that promote ugs and;
- (2)the weakening decisions and actions that undermine ugs.
In both cases, three aspects were taken into account: the managerial actions (what?), the actors or persons responsible (who?), and the underlying reasons (why?). Responses were recorded and their tabulation carried out in an elicitation workshop involving local academics and the authors, complemented by first-hand information gathered from stakeholders in the field and secondary data from literature (Table 11.2). In the Kumasi case study, the measures that favour or disfavour ugs are a blend of top-down and bottom-up mechanisms. Urban green spaces are maintained by different interest groups for varied specific purposes. Because of this, these interest groups may convert ugs to other preferred uses under the influence of different socio-economic, cultural, and/or political factors.
The relevant actors in ugs management are the city authorities, private owners, chiefs, and to a limited extent non-governmental and community-based organisations. In the case of the city authorities, their competencies and roles are regulated by local and national legislation and conventional property rights. These regulations, defined in the most current policy documents, mostly go unapplied despite being comprehensively and theoretically well framed. The authority of the local and central governments over land is limited and lacks enforcement capacity. Hence, the scope of influence in defining and administering ugs is frequently restricted to jurisdiction of, for example, public parks (botanical gardens, zoos, and protected areas) and vegetation in institutional compounds.
Moreover, it is frequently observed that a site originally designated as an ugs is in practice utilised differently or even converted into grey infrastructure, not only by individuals with an interest in the benefits of such a change but also by public authorities with ulterior motives. This is not a new phenomenon. Kumasi has been subject to several city plans since its founding. The 1945 plan, conceived as a quintessential ‘Garden City’ plan in accordance with Howard’s concept, advocated for the creation of a three hundred-metre green belt along stream channels and the establishment of urban parks within Kumasi. However, land use redesignations as a result of population growth and urban sprawl have since rendered these early plans obselete. Most of the designated green belt zone is currently occupied by dense grey/brown infrastructure, such as buildings, roads, and other land uses detrimental to ugs.84 Nevertheless, although Kumasi’s ugs may have declined drastically, its label as a ‘Garden City’ is still widely used with pride by its inhabitants.
The role of chiefs in the Asante region is unique. With the exception of small areas of state land, all land in the region is held in trust for the Asante people by their king, the Asantehene. He allocates land through a network of local chiefs in conjunction with the office of the administrator of stool lands.85 These rights are acknowledged by society and recognised by central government and local authorities.
Some chiefs and their people, however, regard ugs as wasteland; hence protection thereof can be contentious. Even recognised public parks and gardens as well as sensitive wetlands that require mandatory protection may be threatened if land values appreciate and demand for land is high. The government’s policy of non-interference in the chieftaincy weakens its ability to promote and enhance the development of ugs. On the other hand, the power of traditional authorities could be harnessed for the purposes of ugs conservation, environmental protection, and climate change mitigation/adaptation. Citizens swear allegiance to their chiefs; thus urban environmental policies instituted and administered through chiefs can promote a green, climate-resilient city. Indeed, the involvement of chiefs in environmental management is gaining momentum in cities throughout the country.
Although officially regulated mainly by local but also by national authorities, the management of ugs in Kumasi tends to be the de facto responsibility of private land users. Hence, individual behaviour still appears to be the major determinant of both favourable and unfavourable decisions in relation to the greening of the city (Table 11.2). Individual behaviour is generally complex and unpredictable, but a pattern can be observed whereby decisions taken by land users are practical and incentivised by short-term interests. For instance, a substantial number of tree-owning residents in Kumasi acknowledged the direct benefits—shade, air purification, food, and so on—derived from ugs, but stated categorically that they would transform these spaces and erect more profitable structures such as buildings and shops if the need arose. Several household heads resent trees and green spaces in their compounds because of the hazards that they pose. Among other disincentives, trees and green spaces regularly interfere with the roofs and foundations of buildings, litter compounds with leaves and debris, increase fuel loadings and thus the risk of fire, provide habitats for dangerous animals such as snakes and scorpions, increase the risk of incurring damage through falling branches, and may serve as hideouts for criminals. Yet there were also others who wished that they had green spaces in their compounds but who lacked the necessary space. In general, reasons favouring the establishment and maintenance of ugs include:
- (1)beautification—independent of socioeconomic status, property stand of the ugs, and position of authority;
- (2)provision of resources such as food, fodder, fuelwood, etc. (tangible benefits);
- (3)provision of services, e.g. air quality improvement, shade, windbreaks, erosion checks, flood mitigation, etc. (intangible benefits) (Table 11.2).
On the other hand, ugs are threatened by:
- (1)land use conversion towards more profitable uses e.g. houses, public buildings, roads, channels, etc.;
- (2)neglect of landscape plans and ad hoc legislation;
- (3)lack of awareness among urbanites of the value of ugs.
Typical insitutional problems in the Global South also characterise the management of ugs, such as the lack of appropriate legislation or planning and enforcement capacity. Consequently, the importance of ugs may be downplayed in favour of more profitable short-term interests and activities. Although often justified by a lack of financial means, these incentivies are related to systemic malfunctions such as corruption or neglect for the rule of law.
At the level of the individual, decisions concerning management and promotion of ugs can make a considerable positive or negative impact. These decisions appear to be influenced by a person’s background (connection with nature, rural origins), education (knowledge of the importance and roles of ugs), and short-term interests. Although a question that is yet to be thoroughly examined, it is likely that people who live on the outskirts of cities are more likely to have vegetation in their compounds than those who live in the city centre. People living in suburban areas typically belong to the relatively wealthy class, most of whom are well educated and have learnt to appreciate and conserve nature. However, the permanence of such ugs, mainly domestic gardens, cannot be guaranteed as they are predominantly temporary sites awaiting conversion into more lucrative structural use when the economy becomes favourable.
5 Conclusions
Considering the growing awareness of urbanisation, understanding that urban resilience to the impacts of climate change is an important, multidimensional issue accomplished via various means is crucial. Bolstering climate resilience in cities involves several types of activities, and the role of green spaces in this effort must not be peripheral.
This chapter has discussed urban population growth and urban land expansion in Africa in the context of climate change and in relation to the role of green spaces, presenting Kumasi as a case study to illustrate the potential of African cities for climate resilience. Urbanisation unequivocally drives depletion of natural land cover and exacerbates anthropogenic environmental impacts. However, urban green spaces provide opportunities for both reactive (adaptive) and proactive (mitigative) measures to improve a city’s resilience to climate change and its impacts. Through alteration of urban albedo, shading, and evapotranspirational cooling, ugs offer a cost-effective and adaptable means of coping with warming. Urban vegetation interferes with water and air movements on and above land surfaces, lowering the risk of flooding and air pollution. Absorption of ghgs by vegetation (especially trees) plays an important role in air quality improvement and in mitigating both local and global warming. To meaningfully improve urban resilience, ugs must be well planned, adequately integrated into urban space, and underpinned by strong institutions. Under these conditions, abandoned roads, buildings, and other compacted bare surfaces in cities that usually lie idle and unproductive could be converted into green spaces. Vegetation builds up biodiversity, breaks up the compacted concretes in soil, and over time restores ecological equilibrium to such spaces, thus boosting a city’s capacity to cope with climatic stress.
Inadequate implementation of existing legislation and a lack of ad hoc policies leave the initiative to customary and private interests. As such, de facto bottom-up processes determine the existence and management of ugs. Here, the roles of chieftancies (traditional leadership) and individual landowners are particularly crucial. Involvement of the government, traditional leaders, and civil society in defining priorities, streamlining actions, and enforcing policy are essential requisites for sustaining and enhancing green cover in African cities.
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