Spatial distribution and ecological dominance of psidium guajava in the agricultural landscapes of Homa Bay County, Kenya

Psidium guajava L. (guava) is widely cultivated in tropical agro-ecosystems but is increasingly invasive in East Africa. Its rapid spread across smallholder landscapes threatens biodiversity and complicates land management, yet empirical evidence on its ecological dominance and distribution in western Kenya remains limited.This study assessed the spatial distribution, dominance, and diversity of P. guajava in smallholder agricultural landscapes of Homa Bay County, and examined related ecological and socio-economic implications. Surveys design were conducted in three guava-dominated locations—West Lambwe, North East Kanyamwa, and South Kanyamwa—using transects and quadrats to inventory woody species on farms and grazing lands. Species richness and diversity (Shannon and Simpson indices) were calculated, and site differences tested using ANOVA and Kruskal–Wallis statistics. Household data on guava coverage, yields, and management were collected through structured questionnaires. Annual production was estimated from mean area under guava, yield per hectare, and number of producing households. Guava dominated woody plant communities across sites, accounting for 67–86 % of all individuals. North East Kanyamwa showed the highest guava density (85.96 %) and species richness (16 species/ha) but lowest diversity (H′ = 0.724), reflecting severe dominance. West Lambwe recorded the greatest ecological evenness (H′ = 1.147) despite lower richness (10 species/ha). South Kanyamwa displayed intermediate conditions. Estimated annual guava production across the study area was 844.35 tonnes, with South Kanyamwa contributing the largest share (388.65 tonnes). Over 80 % of households reported minimal management, enabling rapid spread. Overall, P. guajava is ecologically dominant in Homa Bay, reducing woody species diversity and homogenizing vegetation. Although important for household fruit supply, its invasive nature poses long-term risks to agro-biodiversity and ecosystem resilience. Integrated management approaches are urgently needed, alongside further research on ecological trends and farmer decision-making.