It contains a finite amount of fresh water, and we can hardly export waste products into outer space. This “walled city, ” however, is able to support billions of creatures, generation after generation.
Цэвэр усны нөөц нь хязгаарлагдмал, хог хаягдлаа гаргаж хаях аргагүй гэдгээрээ манай дэлхий ийм хоттой адилхан юм.