Used to be. Biodiversity in densely human-inhabited areas is ~zero. Apparently the best indicator of overall biodiversity is mycodiversity (ie. fungal diversity). The most varied areas are apparently those with extra moisture and a protected situation, often valleys with a non cardinal orientations and minimal human disturbance at the valley floor. If you want more diversity, actively seek out plants native to your area and plant more of them. Remove lawns, add decaying matter. You'll be surprised how quickly you can obtain impressive results.
FWIW some of my teachers have discovered new orchid species and studied their pollination. It is very common in botany to have no idea what exactly pollinates a species. Ants, insects, birds and mammals are all potential pollinators.