In Tai Wan, TNR was carried out in some districts. The Life Conservationist Association reports that the number of stray animals decreased from 13,281 to 9,515 (nearly 25%) in 2009 and 2010. This shows the effectiveness of TNR in controlling the stray cat population. Therefore, taking into account the environment, society, politics and animal welfare, TNR is the most effective and humane way to solve the problem of stray cat overpopulation. First, on an environmental level, TNR contributes to improving public hygiene in Hong Kong. Most stray cats have the ability to catch rats and cockroaches. This reduces the number of vermin in the community. This also prevents the invasion of vermin from other districts. As a result, public hygiene could be improved. Additionally, the Life Line Animal Organization reports that sterilizing cats could reduce the problem of urine spraying and odor by 87%. The streets will smell less and the environment could be cleaner. Therefore, TNR could effectively solve the environmental problem caused by pests.