One of the biggest drawbacks of the Columbian Exchange was the spreading of disease. During the Columbian Exchange, diseases from the Old World (Europe) were spread to the New World (the Americas). These diseases included things like: smallpox, influenza, whooping cough, and measles. These diseases end up decimating the New World population, as they were never exposed to them before this encounter. Since they had no prior exposure, they had no immunity to these different diseases. Due to this fact, the New World population decreased rapidly.
B. Limited and Vulnerable because only a very small amount of water is available and its running out fast (For example: Cape Town, South Africa is in a drought and lost all potable water)