Tree Species Diversity and Socioeconomic Perspectives of the Urban (Food) Forest of Accra, Ghana

Urban agriculture matters for sustainable development

Urban agriculture can contribute to sustainable development. However, a holistic investigation is lacking to comprehend its positive and negative impacts on the Sustainable Development Goals (SDGs). Our systematic analysis of around 1,450 relevant publications on urban agriculture, screened from 76,000 records, fills this gap. We map and analyze the text in the literature for each SDG target and its associated positive or negative sentiments. Here, we report our results highlighting that urban agriculture is linked to all SDGs, with 142 and 136 targets having positive and negative sentiments. The mapped positive sentiments are around double the negative ones. We identify six leveraging opportunities urban agriculture provides for sustainable transformation with four hurdles to be resolved. Urban agriculture does not inherently contribute to sustainability. Its impacts rely on the adoption of specific practices. Realizing urban agriculture's social, economic, and environmental functions to accelerate SDG progress requires tackling the hurdles.

Greenness and equity: Complex connections between intra-neighborhood contexts and residential tree planting implementation

Associations between neighborhood greenness and socioeconomic status (SES) are established, yet intra-neighborhood context and SES-related barriers to tree planting remain unclear. Large-scale tree planting implementation efforts are increasingly common and can improve human health, strengthen climate adaptation, and ameliorate environmental inequities. Yet, these efforts may be ineffective without in-depth understanding of local SES inequities and barriers to residential planting. We recruited 636 residents within and surrounding the Oakdale Neighborhood of Louisville, Kentucky, USA, and evaluated associations of individual and neighborhood-level sociodemographic indicators with greenness levels at multiple scales. We offered no-cost residential tree planting and maintenance to residents within a subsection of the neighborhood and examined associations of these sociodemographic indicators plus baseline greenness levels with tree planting adoption among 215 eligible participants. We observed positive associations of income with Normalized Difference Vegetation Index (NDVI) and leaf area index (LAI) within all radii around homes, and within yards of residents, that varied in strength. There were stronger associations of income with NDVI in front yards but LAI in back yards. Among Participants of Color, associations between income and NDVI were stronger than with Whites and exhibited no association with LAI. Tree planting uptake was not associated with income, education, race, nor employment status, but was positively associated with lot size, home value, lower population density, and area greenness. Our findings reveal significant complexity of intra-neighborhood associations between SES and greenness that could help shape future research and equitable greening implementation. Results show that previously documented links between SES and greenspace at large scales extend to residents' yards, highlighting opportunities to redress greenness inequities on private property. Our analysis found that uptake of no-cost residential planting and maintenance was nearly equal across SES groups but did not redress greenness inequity. To inform equitable greening, further research is needed to evaluate culture, norms, perceptions, and values affecting tree planting acceptance among low-SES residents.

Urban foraging in Brazilian public greenspaces

Urban foraging, i.e., the gathering of wild edible plants, plays a key role in nature connection within cities. Its integration in planning could contribute to the conservation of urban biodiversity. However, we have little understanding of the interactions between the motivations for and barriers to foraging, and the role of legislation, especially in biodiversity hotspots. Through an online questionnaire and policy review, we explored the practice of urban foraging in Recife, Brazil, across social, spatial and regulatory dimensions. We found that most non-foragers would forage if pollution risks were addressed and knowledge was improved. Foragers collected up to 31 species, none of which are threatened. By integrating the social, spatial and regulatory dimensions of the practice, we highlighted the importance of the local context for targeting foraging incentives. In all, regulation had little impact on where the practice is carried out, and foraging seemed to have little negative impact on biodiversity, as no threatened species were collected and foragers were conscious of their impact. This knowledge can contribute to better integrate the practice of foraging within legislation and develop forager-led greenspace planning and management. In biodiversity hotspots threatened by urban expansion, foraging can contribute to slowing down the biodiversity crisis and improve urban residents' contact with biodiversity.

Assessment of street forest characteristics in four African cities using google street view measurement: Potentials and implications

Accurate information on urban forests of tree sizes, health state, community structures, and spatial distribution is still limited in African cities. Using a Google Street View (GSV)-based tree-size measuring method developed by our team, this paper aims to evaluate street trees of four African metropolitan cities using GSV data. The study compiled a large dataset with 46,016 street trees in 3454 sites in Kampala, Nairobi, Bloemfontein, and Johannesburg. The data including tree size (diameter at breast height, DBH; tree height, TH; underbranch height, UBH; canopy size), tree floristic composition (apical dominance types, broadleaf-conifer-palm leaf, flowering or not), tree health (leaf color, diebacks, dead tree, and bracket-supporting percent), streetside development (lane number, roadside shops, parking vehicle, and pedestrian density), and geolocation (latitude, longitude). These data can be spatially visualized with the help of ArcGIS, and the large dataset favors reliable maps from the street-view level. Data statistics showed that four cities were dominated by broad-leaved, apical dominance, and flowering trees, with a low level of unhealthy leaves and a tiny percentage of dead. The arbor-shrubs-herb structure vegetation dominated all four cities. Kampala had the most slender trees (DBH = 23 cm, TH = 8.4 m), while Nairobi and Johannesburg had the thickest trees (DBH = 38 cm, TH = 8.5-8.6 m). Bare land rates were lowest at 23% in Bloemfontein and highest at 33% in Nairobi. Principal analysis and Pearson correlations showed that these tree variations were closely associated with street development and local land use configuration. By comparing the urban tree data in other regions of the world, we found that the trees in African cities are generally giant but have a lower density (the trees within a 100-m street segment). Our findings emphasized that GSV data is feasible enough for urban forest monitoring in Africa, and the database is helpful for urban landscape planning and management.

Assessment of Street Tree Diversity, Structure and Protection in Planned and Unplanned Neighborhoods of Lubumbashi City (DR Congo)

Street trees are always considered a vital part of urban green infrastructure in urbanized areas through mitigating the negative effects caused by urbanization taking part in human well-being. However, little is still known about their diversity, structure and protection, mostly in Lubumbashi city in the Democratic Republic of the Congo (DR Congo), where the pace of urbanization is not only rapid but also unplanned. In this study, using an inventory, we have characterized the diversity, structure and protection measures of street trees along a land-use planning gradient in Lubumbashi for both planned and unplanned neighborhoods. From the results, a total of 1596 trees were encountered, comprising 40 species, 33 genera and 17 families, mostly dominated by exotic species (65%). In addition, most of the studied trees (63%) belonged to four species only (Jacaranda mimosifolia, Leucaena leucocephala, Mangifera indica, and Acacia auriculiformis) with Leucaena leucocephala and Jacaranda mimosifolia being highly represented in unplanned and planned neighborhoods, respectively. The most abundant diameter classes in the planned neighborhoods were those with at most 10 cm against the classes larger than 50 cm in the planned neighborhoods. In both neighborhoods, trees with protection equipment represent less than 35%. Furthermore, in planned neighborhoods notably, nearly half of the observed equipment is in a good condition. Despite the benefits associated with street trees, there is a need to reduce the proportion of exotic tree species by planting native utilitarian tree species.

The mid-domain effect of mountainous plants is determined by community life form and family flora on the Loess Plateau of China

The mid-domain effect (MDE) explains altitudinal patterns of species diversity of mountainous plants at different elevations. However, its application is limited by the species life form and family flora in different layers of plant communities. To verify the MDE hypothesis at the plant community level, we chose a mountain with representative characteristics of the study area in the east of the Loess Plateau, China, such as obvious elevation (from 1324 to 2745 m) and latitude (from 36° 23' to 39° 03') gradients and considerable vegetation types (mainly coniferous and broad-leaved forests). We measured the life forms, families, and species diversity indices of tree, shrub, and herb communities along different elevations. We determined that the family numbers of the herb and shrub communities presented unimodal patterns across an altitudinal gradient, and the highest values occurred at intermediate elevations. The importance values of dominant families in the shrub and tree communities presented unimodal patterns, but the lowest values occurred at intermediate elevations. The species diversity indices of the herb, shrub, and tree communities conformed to unimodal change patterns following an altitudinal gradient, but the greatest diversity occurred at high, low, and intermediate elevations, respectively. At higher elevations, forbs and grasses grew well, whereas sedges grew well at lower elevations. Responses of different tree life forms to the altitudinal gradient were greater for evergreen coniferous tree species than for deciduous coniferous and deciduous broad-leaved tree species. We concluded that the MDE hypothesis of species diversity for mountainous plants is influenced greatly by the community life form and family at the plant community level in a temperate semi-arid region of the Loess Plateau, China. This conclusion tested and modified the MDE hypothesis and may be valuable for fueling prediction of biodiversity models and for the comparison with similar studies in arid and semi-arid mountainous regions.

Rediscovering the Contributions of Forests and Trees to Transition Global Food Systems

The importance of forests to safeguard agricultural production through regulating ecosystem services such as clean water, soil protection, and climate regulation is well documented, yet the contributions of forests and trees to provide food for the nutritional needs of the increasing human population has not been fully realized. Plants, fungi, and animals harvested from forests have long provided multiple benefits—for nutrition, health, income, and cultural purposes. Across the globe, the main element of “forest management” has been industrial wood production. Sourcing food from forests has been not even an afterthought but a subordinate activity that just happens and is largely invisible in official statistics. For many people, forests ensure a secure supply of essential foods and vital nutrients. For others, foraging forests for food offers cultural, recreational, and diversified culinary benefits. Increasingly, these products are perceived by consumers as being more “natural” and healthier than food from agricultural production. Forest-and wild-sourced products increasingly are being used as key ingredients in multiple billion dollar industries due to rising demand for “natural” food production. Consumer trends demonstrate growing interests in forest food gathering that involves biological processes and new forms of culturally embedded interactions with the natural world. Further, intensifying calls to “re-orient” agricultural production provides opportunities to expand the roles of forests in food production; to reset food systems by integrating forests and trees. We use examples of various plants, such as baobab, to explore ways forests and trees provide for food security and nutrition and illustrate elements of a framework to encourage integration of forests and trees. Forests and trees provide innovative opportunities and technological and logistical challenges to expand food systems and transition to a bioeconomy. This shift is essential to meet the expanding demand for secure and nutritious food, while conserving forest biodiversity.

Characterization of Urban Greening in a District of Lecce (Southern Italy) for the Analysis of CO2 Storage and Air Pollutant Dispersion

This paper is devoted to the assessment of urban greening effects on two important ecosystem services, i.e., air quality and CO2 storage, including the corresponding economic impacts in a real urban area, i.e., a district located in the Mediterranean city of Lecce (southern Italy). Two tools were employed, i-Tree Canopy and the computational fluid dynamics (CFD) microclimate model ENVI-met. i-Tree Canopy allowed fully determining the land-cover percentage on the basis of different ground cover classes and obtaining an estimate of annual values of CO2 storage, air pollutant removal, and economic benefits in the presence of urban greening. The estimate in i-Tree Canopy considered only the amount of greening; therefore, air pollutant removal estimates were only potential. As the vegetation was located in street canyons, its interaction with local meteorology and urban geometry strictly affected the dispersion of nitrogen oxides (NOx) (taken here as an example) as obtained from ENVI-met simulations. In ENVI-met, both deposition/absorption and aerodynamic effects were considered, and local increases in concentration were found in the district. The analysis of results obtained from different tools (one complex (CFD model) and the other simple (i-Tree model)) showed the error associated with the simple model in the computation of impacts if the interaction among the vegetation characteristics, the meteorological conditions, and the urban geometry was neglected; however, it also uncovers a novel approach for comprehensively characterizing a given area in terms of its vegetation cover, CO2 storage, and economic benefits, as well as local effects on air quality. This study is set in a broader context aimed at assessing the air quality in urban canopies of Mediterranean areas characterized by the presence of narrow street canyons where pollutants can accumulate due to ineffective air exchange with the above atmosphere.

Urban Forestry in Brazilian Amazonia

Urban forests provide multiple benefits in improving people’s lives and can be an important tool for achieving the goal of carbon neutral cities. In this study, we analyzed the diversity of plant species from urban forests in cities in the Brazilian Amazonia, based on data from scientific articles, through a systematic literature review. Our analysis revealed that 530 taxa, of which 479 were identified at the species level and 51 at the genus level, covering 38,882 individuals were distributed in 29 cities. The three most frequent species were Ficus benjamina, Mangifera indica, and Licania tomentosa. Exotic species were more frequent than native. The three most frequent species had almost 42% of the inventoried individuals. The choice of species has been made mainly by the local population, without monitoring by the public authorities. Recommendations for sustainable management of urban forests in Amazonia include investing in training of management bodies, periodic inventories, and awareness actions about the benefits of urban green infrastructure and on the advantages of native species. Policies for the sustainable management of urban green areas are necessary. The municipal governments must continuously monitor indicators of urban ecosystem services and provide financial resources for maintaining and increasing those area rates per person.