From farmers to power-brokers, now many people appreciate wetlands. Science has led this attitude adjustment. Since the mid twentieth century, biologists, hydrologists, geologists, and other scientists have been studying wetlands to understand how they function, and what they contribute to ecosystems, and to human health and economy. For example, wetlands act like giant sponges, absorbing water during floods and storms. This water, instead of washing downstream and loading water with sediment, instead slowly soaks into the ground to recharge aquifers and other sources of ground water. As water collects in wetlands, this ecosystem cleans the water. Sediments settle out as the water slows; the soil particles bind with pollutants, and some plants absorb the toxins.