Introduction Karachi is the largest city of Pakistan. It is the main financial center and also the largest seaport in the country. The city has an estimated population of about 15 million people which makes it one of the world’s major cities in the world in terms of population. Karachi harbors numerous industrial and economic activities. Thus, it forms the center for banking and industry in Pakistan. The major corporations present in this city are automobile industry, textile, shipping and medical research. This paper discusses how the emergence and development of this city has impacted the environment and the ecosystem throughout the years. Ecology of the city Karachi is a city built at the cost of the Indian Ocean. This means that the city has major interactions between the human population, the fauna and flora, and the environment of the city. The Karachi coast has a diversity of flora such as green sea weed that grows at the rocky shores (Ghani para. 4). These weeds are a source of food and shelter for the epifauna of the coast. Karachi’s industries cause a great impact on the environment. The industries discharge their industrial effluents to the coastal areas. These cause the coastal area of Karachi to be badly affected by the industrial and untreated sewage at the harbor. A survey done on the sea water of Karachi harbor reveals that the industrial effluent and untreated sewerage causes eutrophication of the sea water. This means that the eutrophication that causes growth of microorganisms such as bacterial has a detrimental effect on other sea dwelling organisms. The effluent is usually carried along to the Karachi harbor through the Lyari River. Since the tides of the Karachi harbor are semi diurnal type, the effluent is not completely flushed out. This means that there is a poor circulation condition that causes hydrogen sulfide to be produced. The hydrogen sulfide is known to cause stress on the marine organisms (Saleem 1). In addition, poor development of infrastructure is believed to increase the impervious surface area of the city. This causes flash floods and run-off that may increase erosion and non-point pollutants if the water is not channeled properly. It is also important to note that impervious ground reduces the rate of groundwater recharge (URC 3). Other pollution sources include the release of green house gases by the Karachi industries. Carbon dioxide and sulfur dioxide are produced by these industries thereby contributing to global warming. The increased number of motor vehicle usage causes excessive release of carbon monoxide which is harmful if inhaled by humans (Kumar and Chaturvedi 172). The effects of the growth of this city are more disadvantageous especially if not checked. Thus, the increased in the demand for housing in Karachi also creates a poor environment that the people are exposed to live in. It is worth noting that the city is trying to tackle these environmental problems through various programs that involve industrial and solid waste management. Solid wastes generated by the city are managed by way of recycling. The informal sector is involved in performing the functions of waste management. The waste management program has helped reduce the negative impacts of waste on the environment such as diseases and eutrophication. Conclusion Karachi is the largest city of Pakistan. It is the main financial center and also the largest seaport in