This blog usually deals with typical conflict caused or inspired by natural resources. Population growth is essentially only a problem because of the limited space available hence I think it's fair to say the problems it causes are also 'environment problems'. The closer we live the more we expose each other to our diseases and the various toxins we produce, consume and waste. The more people we are the more food we need - the more biosphere we consume and industrialize, the closer we keep our livestock and the more of us go hungry. And the more hazardous the environment we live in, the more likely we are to kill our neighbor and run off with his.
The top three killers
Blowing soil can contain many different pathogens - tuberculosis (TB), anthrax et cetera. Industrialized agriculture and deforestation are the main reasons for erosion by wind of contaminated soil. Just an example of how the various issues are intrinsically linked. Right now about 2 billion people (absurd) are infected with TB and 3 million people will die each year.
Hastily erected housing and slum suffer from bad sanitation. Bad sanitation - or none at all - will cause various health issues. But 2.5 billion people lack adequate sanitation. Proper sanitation could have hindered most of the 4 billion annual diarrhea infections as well as most of the 2.1 million deaths. Totally, lack of sanitation is estimated to kill more than 5 million people each year by various means.
People who don't eat right or just not enough are more susceptible to many other problems. The soil erosion mentioned, caused by industrialized agriculture, is not only spreading diseases and diminishing our arable land area - crop productivity per area is drastically reduced. Causing more malnutrition. 6 million children die from malnutrition issues each year. 2.5 million die from vitamin A deficiency and 9 million from iron deficiency. A staggering total of about 18 million people dies from malnutrition each year.
Honorable mention is deserved in the case of air pollution problems (3 million), asthma (2.1 million), malaria (1.2-2.7 million) and measles (1.1 million).
But we're getting better, right?
On the Bjørn Lomborg show, perhaps. In the real world, no. From 1970 to 2002 the number of cancer cases climbed from 331,000 to 563,000 in the USA alone; mostly caused by chemical pollutants. From 1940 to 2007 women's risk of breast cancer went from 1/22 to 1/7. From 1971 to 1986 malaria increased by 76% in Brazil; mostly caused by deforestation. From 1950 to 2007 the number of malnourished people went from about 500 million or 20% to 3.7 billion or 60%. Iron intake is going down along with the rest of the measures of food quality. Antibiotics go useless as pathogens evolve resistance do to our overuse. I could go on and on...
New problems in a new environment
SARS evolved because people and livestock crowded in China. Almost the same story with avian flu. Neither has killed that many people yet, but they are new problems with high mortality rates.
Construction of dams has increased the number of snails that host schistosomiasis [Wikipedia] and climate change is creating an environment more suitable for them. Schistosomiasis has now spread to areas where it was never seen before, infecting more than 200 million people, killing as many as 200,000 annually. Global warming also helps spread malaria and many other diseases. Our massive consumption of fossilized fuels seems to be at the root of so many of our problems. (And what do we do? Use more of it waging wars over the remaining sources of it.)
Salmonella, E. coli and Campylobacter microbes infect our increasingly crowded livestock while new diseases evolve in unsanitary industrialized slaughterhouses.
While I think I insist HIV isn't an environmental issue, infected people help spread numerous other diseases. Wars and urbanization undoubtedly help spread both. Our biosphere is a complex system. Any change in a complex system will produce numerous other changes and will always cause crisis somewhere. I wrote it already: I could go on and on...
Pimentel, D., Cooperstein, S., Randell, H., Filiberto, D., Sorrentino, S., Kaye, B., Nicklin, C., Yagi, J., Brian, J., O'Hern, J., Habas, A., Weinstein, C. (2007). Ecology of Increasing Diseases: Population Growth and Environmental Degradation. Human Ecology, 35(6), 653-668. DOI: 10.1007/s10745-007-9128-3