Species Diversity

What is it? A diverse urban ecosystem is crucial to prevent the dominance of just a few tree species. This not only enhances aesthetic value but also ensures the urban forest is more resilient to pests and diseases.

The Standard The widely accepted standard is the 10/20/30 Santamour rule, which states that no single species should make up more than 10% of the population, no single genus more than 20%, and no single family more than 30%. This corresponds to a Gini-Simpson Index value of 0.9 to 1.0. While such high values are rare in urban environments, striving for them improves ecological resilience.

Current Status Yerevan's current Gini-Simpson index is 0.7784 which indicates a healthy level of diversity. While there is room for improvement, Yerevan is avoiding the "green desert" trap, making it unlikely that a single pest outbreak would catastrophically impact the city's greenery.

Note: This index is calculated based on trees inspected by volunteers. Although the dataset currently covers approximately 10,000 trees, this sample size is sufficient for a reliable diversity estimate.

Important: This value reflects the city-wide average. While the city's aggregate diversity is robust, individual districts may still lack diversity and remain vulnerable.