Average US grain yields per hectare have increased from 1.5 tons in 1950 to 4.4 tons in 1990. The implanted gene might protect the plant from insects or plant diseases, or might increase the yield or growth rate of the plant. However, there are concerns about placing genetically engineered crops in the environment. Modern fishing methods are so effective that they are depleting fish stocks to commercial extinction. Sea turtles, dolphins, whales, and seals are killed by methods such as long lines, purse seines, trawl bags, and drift nets.
Fish stocks can recover if managed carefully.
Many nations declare 320 km of open ocean nearest their shorelines as territorial waters. Some nations manage fishing in territorial waters while others allow unrestricted access to fish stocks to citizen run fishing boats.