[originaltext] The world will need to double food production within the next

The world will need to double food production within the next three decades in order to feed a rapidly and increasingly growing population, which is going to grow from 7 billion today to 9 billion. A United Nations report says reaching that goal will require major increases in high-efficiency livestock operations for both meat and dairy production. The report also says that intensive livestock operations can cause serious ecological risks. And that’ s why environmental critics are calling instead for reductions in global livestock production, and urging people to consume less, not more, meat in their diets. Feeding today’ s population is a challenge for an already-stressed environment. The challenge is how to ensure food without increasing animal numbers and having an impact on lands and our resource bases. More than half of the agricultural land in the world is used to raise and feed livestock. Those farm animals are also responsible for 18 percent of the greenhouse gases released into the atmosphere every year. Experts agree that the next few decades will present a puzzle, how to feed nine billion people without destroying the planet in the process.
1. Why is increase in livestock production necessary?
2. What does the word "challenge" mean in the news item?