Urban ecology is the study of the relationships between living organisms, human communities and the physical environment within urban areas. Cities are highly modified ecosystems where natural landscapes are transformed into buildings, roads, industries and other infrastructure. Urbanisation provides employment, education, healthcare and other opportunities, but rapid and unplanned urban growth creates serious ecological challenges. These challenges affect biodiversity, natural resources, environmental quality, human health and the overall sustainability of cities. One of the major challenges of urban ecology is the rapid loss of natural habitats. Expansion of cities often requires the conversion of forests, wetlands, agricultural land, grasslands and other open spaces into residential colonies, commercial centres, roads and industrial areas. Habitat destruction and fragmentation reduce the availability of food, shelter and breeding grounds for plants and animals. Many species are unable to adapt to such rapid changes and their populations decline. Fragmented green spaces also restrict the movement of wildlife and reduce ecological connectivity. Loss of biodiversity is another important challenge. Urbanisation generally favours a small number of adaptable species while many native species disappear. Birds, insects, small mammals, amphibians and native plants are particularly affected by habitat modification. The replacement of diverse natural vegetation with ornamental plants and monoculture landscapes further reduces biodiversity. Declining biodiversity can weaken ecosystem functions such as pollination, seed dispersal, pest regulation and nutrient cycling. Air pollution is a serious ecological problem in cities. Vehicular emissions, industries, construction activities, power generation and burning of waste release pollutants such as particulate matter, nitrogen oxides, sulphur dioxide, carbon monoxide and other harmful substances. Poor air quality affects vegetation and urban wildlife as well as human health. Vegetation exposed to pollutants may experience reduced growth and physiological stress. Air pollution also interacts with climatic conditions and can contribute to the formation of smog and other environmental hazards. Water pollution and water scarcity present another major challenge. Urban areas generate large quantities of domestic sewage, industrial effluents, solid waste and stormwater runoff. Where sewage treatment is inadequate, pollutants enter rivers, lakes, wetlands and groundwater. Excess nutrients can cause eutrophication, resulting in excessive algal growth and depletion of dissolved oxygen. At the same time, rapid urbanisation increases demand for