ISA Certified Arborist Practice Exam 2025 - Free ISA Arborist Practice Questions and Study Guide

Tree diversity in a landscape primarily benefits the ecosystem by reducing vulnerability to pests and diseases. This concept is rooted in ecological principles where a variety of tree species provides a more resilient and balanced ecosystem. When multiple species are present, the likelihood that a specific pest or disease can spread and cause widespread damage is significantly decreased. Different tree species often have varying levels of resistance to certain pests and diseases, which helps to ensure that if one species is affected, others within the ecosystem can remain healthy and continue to thrive.

Additionally, a diverse tree population can support a wider range of wildlife, as different species provide varied habitats and food sources. This increases the overall stability of the ecosystem, contributing to its ability to recover from disturbances.

In contrast, visual diversity is important for aesthetic purposes but does not directly influence ecosystem health. Uniform growth patterns are often seen in monocultures and can lead to increased susceptibility to specific threats. Finally, while maintenance costs can vary, increased tree diversity generally does not inherently result in higher costs; rather, it can promote a healthier and potentially lower-maintenance landscape in the long term.