You are failing to take into account the steady decline in the global birth rate since the mid 1980s. While we are at 1.1% now, we were over 2% in the 60s and have steadily dropped from 1.6% in 1990 and will go under 1% by 2020 and hit 0.5% by 2050 at the current rates. The current prediction for an extra 2 billion is 30 years time and to reach a peak of 11 billion in the early 22nd century before beginning to drop off.
The driving forces behind 3+ children were lack of basic education, religious beliefs and poverty. As the information evolves, the first two factors are fast disappearing. People are fast gaining an understanding of the growth issues globally and are adjusting their behaviors because of that understanding.
What may require intervention are the farming processes and the distribution of foods. The calorie requirements in developed countries have dropped because of the less manual labour nature of the economies, but the calorie consumption has increased dramatically. That is something that should be rectified both for the health of the population and to increase the availability of food in areas where needed. Easy access to higher density cultivars and reversion to soil management techniques from previous centuries is also essential. This might need a breaking of the business models of food, fertilizer and seed companies, but we don't like Monsanto anyway, don't we.
There is a growth issue and a food/water issue, but it isn't an exponential issue.
