(i) Domestic gardens serve as a source of food (contributing to household nutrition and food security), herbs (medicine), and modest monetary gains from the sale of garden produce (augmenting household income).

(ii) Communal gardens provide means of social interaction, thus enhancing social capital: the appropriation of open communal green spaces and garden products for religious activities and community engagements deliver socio-cultural benefits.

(iii) Flood regulation and local climate moderation, including wind and temperature control, were reported by residents. Experimentation with Vertical Greening Systems within a low-income community in Lagos shows the possibility of reducing indoor air temperature by up to 2.3°C across wet and dry seasons (Akinwolemiwa et al., 2018).

(iv) Natural ecosystems complement available but inadequate basic services and serve as a quasi-amenity. For instance, riparian spaces support recreational activities in the absence of formal parks (See Figure 1). The stream provides water, making up for shortfalls in potable water supply from communal taps. In the absence of electricity connections, firewood used for fuel is harvested from trees within and around communities.

(v) Aesthetics: beautifying the home and its immediate environment through different plants.

(i) Insecure tenure in informal settlements manifests itself through lack of proper title to land, eviction threats, high percentage of renters, and concentration of migrants. These often discourage substantive long-term investment in gardens and other forms of green spaces.

(ii) Space limitations: Many households recognize small plot size as a hinderance to domestic gardening. Increasing pressure on limited land available for housing may not guarantee increased plot size in future.

(iii) Soil conditions: Some communities have contaminated soil (from dumping and sewerage disposal), saline soil (for coastal areas), or already compacted soil. These do not ordinarily support vegetation growth.

(iv) Socio-economic struggles: Poor households' considerations for income generation tend to override interests in greening their dwellings. An example is preference for rentable backrooms to well-kept productive home gardens.

Informal areas are often not included in municipal plans and development of amenities including green spaces such as parks. This situation excludes the residents from benefiting from the positive externalities of green infrastructure. In response, make-shift parks self-built from recycled materials are a notable feature within some settlements. See examples in Figure 2.

The approach taken for the development of green infrastructure must be reconsidered. There is evidence of residents' willingness to pay for green infrastructure, namely communal gardens (allotment), riparian corridor rehabilitation and maintenance, a community park, and children's park (Adegun, 2017b). Table 1 shows the response across a range of possible developers. There is lack of willingness to pay for spaces developed by governments compared with those of residents and NGOs. This level of willingness shows that non-state actors must be engaged to contribute to green infrastructure development.

In-situ upgrading of informal settlements creates opportunities for development of community-scale green infrastructure. An example in Johannesburg (Ruimsig settlement) reflects opportunities that come with these kinds of intervention (Adegun, 2018b). In-situ upgrading, more than relocation to far-flung new housing, is a better approach at addressing the bundle of sustainability considerations (environmental, social, and economic) for households in informal settlements.