Some scientists have proposed taking advantage of this fact through geoengineering, or deliberately intervening in the climate system using technology. Much like forests on land, phytoplankton in the ocean serve as "carbon sinks" because they take up carbon dioxide and then take that carbon with them into the deep ocean when they die. (To prove this, scientists in the early 1990s dumped iron across a 64 square kilometer region of the open ocean and quickly observed a doubling in the amount of phytoplankton biomass.) For the trillions of phytoplankton in Earth's oceans, iron is a "limiting nutrient," meaning the available amount of it is a natural check on these creatures' population size. However, iron is relatively rare in the open ocean, since it mainly comes in the form of soil particles blown from the land. Humans need it to make new blood cells, while many plants need it to perform photosynthesis. Iron is a vital nutrient for nearly all living things. When we reduce our levels of iron oxide emissions-which we ultimately have to, to protect human and animals from inflammation and other adverse health effects-it will necessitate an even more drastic reduction in pollution to avoid the effects of climate change, the researchers warn. If that sounds like a good thing, it isn’t. For instance, iron emissions from coal burning and steel smelting could actually be helping the oceans thrive and suck up more atmospheric carbon, according to new research. But they’re just beginning to untangle the effects of some of the other pollutants we produce. Scientists now understand how the carbon and methane emissions from our cars, livestock and electricity use are helping drive dramatic shifts in our climate through their contribution to the greenhouse effect. Emissions from steel production in eastern China are fertilizing nearby oceans.