FORTY YEARS after the first Earth Day, our world is in crisis. While climate change is the greatest public health challenge of our time, it also presents the greatest opportunity – an unprecedented opportunity to build a healthy, prosperous, clean environment now and for the future.
Earth Day 2010  (April 22) was                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   a pivotal opportunity for individuals, corporations and governments to join together for Mother Earth. Join the more than 1 billion people in 190 countries that are taking action for Earth Day. With an estimated 1 billion people worldwide living in chronic hunger, and global food stocks at historically low levels, it is also fitting to acknowledge the importance of the environment and the role of sustainable natural resources management for survival.
Without careful attention to these matters, substantial decreases in food production by 2050 are predicted, due to population pressures on existing agricultural land, water scarcity and pollution, over-exploitation of fish stocks, and climate variability. At the same time, there could be increased pressure to convert critical forests, wildlife habitats, and fragile lands to agricultural production.
The Relationship between Population and Environmental Sustainability
It is anticipated that the world’s population will increase by 50 percent by 2050. Of this growth, 99 percent will take place in developing countries, and more than 90 percent of the growth will be concentrated in the poorest of these countries. Countries where overall birth rates and rates of unintended pregnancy remain high are now seeing explosive growth in urban slums, a failure of the state to keep pace with educational demands and in some cases, persistent low status of women.
Ensuring the world’s people can have a sustainable future not only includes protecting the natural world, but also understanding the fragile balance that exists between humans and the environment. Developing countries significantly add to the human population, accounting for 95 percent of the world’s annual population increase.
Every day, 214,000 babies are born; every week, population increases are equivalent to that of San Francisco’s population; every 15 months, population increases are equivalent to that of Mexico’s population. At this rate of growth, the world’s people will face shortages in food and water supplies, deforestation, and poorly managed urbanization and industrialization. All pose enormous threats to the environment and to human life.
Ultimately, the health of the planet and its inhabitants depends on the reproductive choices we make today. Family planning programmes go hand-in-hand with sound environmental management. More than 120 million women want to plan their families, but lack the information and services to do so. When family planning information and services are widely available and accessible, couples are better able to achieve their desired family size. Being able to plan family size not only has a direct impact on the well being of families, but also contributes to slower population growth and to conservation of natural resurces.
10 Population Health Facts
*   Between 1995 and 2005 alone, the urban population of developing countries grew an average of 1.2    
million people per week or around 165,000 people per day.

*   Evidence from 47 countries on child health outcomes shows higher socioeconomic inequality in urban       
areas compared to rural areas.

*   One in three urban dwellers or 1 billion people worldwide lives in slums.

*   Around 32 per cent of urban residents in developing regions lack improved sanitation. Globally, it is
estimated that 3 per cent of all deaths, and most diarrheal disease are attributable to the lack of improved   
drinking water sources, sanitation, and adequate hygiene.
*    About 25 per cent of city dwellers in developing countries, and 70 per cent in least developed countries use solid fuels for heating and cooking, causing indoor pollution. This greatly increases the risks of respiratory disease, especially in children, and exacerbates outdoor air pollution 
*    Tuberculosis (TB) incidence is much higher in big cities. In New York City, TB incidence is four times the national average. Incidence of TB in some parts of London is as high or higher than in China. The situation is no different in resource-poor countries: 45 percent of TB cases in Guinea live in Conakry; 83 percent of TB cases in the Democratic Republic of the Congo live in cities.
*    Developing country cities are particularly vulnerable to health hazards from climate change. In particular, the coastal location of many major cities makes populations more vulnerable to extreme weather and rising sea levels.
*    Heat waves also place cities at risk of the “heat island” effect, where temperatures may be as much as 41°–52° F (5–11° C) warmer than surrounding rural areas due to dense urban geography and energy sources.
*    Prevalence of HIV in generalized epidemics is generally higher in urban areas; population-based household surveys indicate that prevalence is 1.7 times higher in urban than in rural areas.

*    The rapid growth of cities has increased the visibility of unequal access to skilled care at birth and to emergency care for urban women.
Source:  WHO