Street tree communities reflect socioeconomic inequalities and legacy effects of colonial planning in Nairobi, Kenya

Abstract

Street trees provide ecological and social benefits that sustain urban life, yet their distribution frequently mirrors socioeconomic inequalities, meaning underprivileged social groups also have fewer trees. The distribution patterns of urban trees are least documented in the cities of rapidly evolving middle-income countries. We assessed whether street tree abundance, size, condition, diversity, and composition vary across census-derived socioeconomic strata in Nairobi, Kenya. We sampled 2047 trees across 12 neighborhoods, covering 24 km of street, then used linear regression to understand how socioeconomic strata relate to street tree characteristics. We found substantial disparities in tree abundance, with affluent areas harboring 91.5 % of the trees sampled. Low-income areas and informal settlements had comparably few trees. Mean diameter and condition did not vary across socioeconomic strata, but high-income, formerly European neighborhoods had a higher proportion of small trees, indicating a bias in recent urban greening investments further benefiting these areas. Species diversity followed a similar pattern of inequality. High-income neighborhoods had over 30 % higher species richness and diversity than low-income areas. Even so, lower income neighborhoods exhibited greater differences in street tree community composition, and a higher proportion of trees that bear edible fruit or are used in traditional medicine. Overall, our results reveal pronounced spatial inequality in the distribution of street trees in Nairobi, reflecting not only socioeconomic differences but the enduring legacies of colonial planning.