Sydney boasts a vibrant and diverse ecology characterized by a variety of plant communities and a wealth of wildlife. The most prevalent vegetation types in the region include grassy woodlands—often referred to as savannas—and pockets of dry sclerophyll forests. These forests are primarily composed of eucalyptus trees, casuarinas, melaleucas, corymbias, and angophoras, accompanied by shrubs such as wattles, callistemons, grevilleas, and banksias. The understory typically features a semi-continuous growth of grasses, which often have rough, spiky leaves due to the area's low soil fertility.

In addition to the dry sclerophyll forests, Sydney contains areas of wet sclerophyll forests, particularly in the wetter, elevated regions to the north and northeast. These forests are distinguished by their tall, straight canopies and a moist understory filled with soft-leaved shrubs, tree ferns, and various herbs.

The predominant vegetation community within the city is the Cumberland Plain Woodland, located in Western Sydney. This is followed by other significant ecosystems such as the Sydney Turpentine-Ironbark Forest in the Inner West and Northern Sydney, the Eastern Suburbs Banksia Scrub along the coastline, and the Blue Gum High Forest, which is sparsely present in the North Shore. Notably, all of these forest types are critically endangered, underscoring the need for conservation efforts.

Sydney's ecological landscape is also home to a rich avifauna, with dozens of bird species residing in the area. Common species include the Australian raven, Australian magpie, crested pigeon, noisy miner, and pied currawong. However, the city also hosts several introduced species such as the common myna, common starling, house sparrow, and spotted dove, which have adapted well to urban environments.

Reptile species are abundant, predominantly comprising various skinks. The city is also home to a few notable mammal species, such as the grey-headed flying fox, along with the infamous Sydney funnel-web spider. Furthermore, Sydney’s coastline and harbour support a vast diversity of marine life, enriching the city's ecological tapestry.

In summary, Sydney’s ecology is a complex interplay of native and introduced species within a rapidly urbanizing landscape. Protecting and preserving these ecosystems is crucial for maintaining the city’s biodiversity and the ecological health of its environment.