Context-Specific Use of Prosopis juliflora in Riyadh

Alexandra von Bieler
May 21, 2026

Rethinking “Invasive”?

Executive Summary

The classification of Prosopis juliflora as an invasive species in global and regional plant lists should not automatically justify its exclusion from urban planting strategies in Riyadh. Over more than 50 years of observed use, there is no substantive evidence of invasive behaviour under local environmental conditions.

From the seventies of the last century Prosopis juliflora had been planted in various locations in Riyadh from the city centre (parks and gardens), next to roads (King Fahad Road e.g.), Diplomatic Quarter (Parks and extensive green of the earth berm), Wadi Hanifah (the urban part and there also to try establishing trees in highly disturbed areas and high-water level). Even in Wadi Hanifah there is no evidence at all of any sign of invasive behaviour.

In comparison to Acacias (Vachellias) Prosopis’ canopy is dense and wide, the foliage is greener and the thorns are small. With proper and professional pruning, the canopy is steady and stable. So next to its other values such as resistance against heat and providing shade, its appearance is also appealing.

The number of trees suitable for the hyper harsh and arid climate of Riyadh city is quite limited. Therefore a context-specific policy approach is recommended, allowing controlled use of this species where it demonstrably contributes to urban resilience, environmental quality, and public wellbeing.

1. Background

Prosopis juliflora is widely recognized as invasive in certain regions of the world, particularly where climatic and ecological conditions support rapid spread. As a result, it is frequently included in precautionary “blacklists.”

However, such classifications are typically based on global or regional risk assessments, which may not reflect site-specific ecological realities, particularly in hyper-arid environments such as Riyadh.

2. Local Evidence from Riyadh

Empirical observation over approximately five decades indicates that:

The species has been confined to planted locations within the urban fabric

No meaningful natural spread or colonization has been observed, even in proximity to water bodies such as Wadi Hanifah

The tree performs reliably under extreme arid conditions, contributing to:

Urban shading

Reduction of heat island effects

Improvement of air quality

Enhancement of public green spaces

This long-term, real-world performance strongly suggests that Prosopis juliflora does not exhibit invasive characteristics in Riyadh’s environmental context.

3. Environmental and Urban Value

In a harsh desert climate, species capable of thriving with limited water and high temperatures are essential. Prosopis juliflora offers:

Dense, persistent canopy providing effective shade and thermal comfort

High tolerance to drought and poor soils

Contribution to urban liveability and wellbeing

Support for expanding green infrastructure in a resource-constrained environment

Excluding such a species without locally relevant evidence may unnecessarily limit the palette of viable urban trees.

4. Risk Assessment Considerations

The precautionary principle should be applied proportionately. In the case of Riyadh:

Key drivers of invasiveness observed elsewhere (e.g., seasonal rainfall, dispersal mechanisms) appear to be absent or limited

Over 50 years of exposure have not resulted in detectable ecological spread

The risk of invasion under current conditions can therefore be considered low based on available evidence

5. Management Considerations

Observed challenges related to Prosopis juliflora are primarily management-related, not ecological:

Excessive or improper pruning can destabilize tree structure and increase branch failure risk

Appropriate arboricultural practices can effectively mitigate these issues

This reinforces that the species can be safely integrated when properly managed.

6. Policy Recommendation

Rather than a blanket prohibition, the following approach is recommended:

Conditional Approval
Permit the continued use of Prosopis juliflora in defined urban contexts within Riyadh

Monitoring Framework
Establish periodic ecological monitoring to detect any signs of:
- Natural regeneration outside planted areas
- Unexpected spread patterns

Management Guidelines
Implement best-practice standards for pruning and maintenance

Site-Specific Evaluation
Restrict or reassess use only in locations where environmental conditions may change (e.g., newly irrigated natural corridors)

7. Conclusion

A uniform classification of Prosopis juliflora as invasive does not adequately reflect its documented behaviour in Riyadh. Policy decisions should be guided by local evidence and long-term observation, not solely by external classifications.

Maintaining access to resilient, high-performing species is critical in arid urban environments. A balanced, evidence-based approach will better serve both ecological integrity and the wellbeing of Riyadh’s residents.