Washington ( CNN ) -- Oil could turn Gulf marshlands into open water and affect millions of migratory birds for generations , Tom Moorman , the senior science official and leader of the oil spill task force for Ducks Unlimited said Friday . It has taken more than 50 years for the plant root network holding the marshlands together at the base of the Mississippi River to form , he said at a briefing for reporters . If destroyed , the marshlands would flood and become open water , he added . Louisiana marshland has shrunk from 3 million acres to 1.2 million acres , or 40 percent , since the turn of the century , and toxic oil would accelerate that , he said . He said that more than 13 million migratory birds come to the Gulf marshlands each winter , though the exact number is hard to determine . If oil enters and lingers in the Gulf marshlands through the late summer and fall , it will affect millions migratory birds that rely on marshland resources for the winter , Moorman said . `` We ca n't even estimate the number ( of birds ) , '' he said . `` It 's just that kind of a place . '' It 's difficult to to implement restoration efforts now when they do n't know where the oil is going or what the impacts are right now , he said . `` In my career of 19 years I 've never seen a situation with so much uncertainty , '' he said . Ryan Lambert , a fishing tour captain for Cajun Fishing Adventures , spoke at the same briefing about watching oil wash away 29 years of knowledge learned on the job . `` My books are just red with cancellations right now , '' he said . Once oil enters the wetlands , it 's hard to get out so prevention is key , Moorman said . Cleanup efforts are in action in marshland areas already hit by oil , he said . For the birds , oil could kill them quickly by covering their plumage and preventing temperature control , slowly poison them through their food supply of oysters , insects and plants , or inflict `` sublethal impacts '' by causing reproduction problems when they head back north for winter , Moorman said . If necessary , Moorman said , flooding agriculture areas nearby should be considered in the hope some birds would migrate to those areas this winter . Even if they created manmade marshes , however , they ca n't control the birds , he said . Lambert called for sediment deposits to rebuild the marshlands so that nature could heal itself . Ducks Unlimited and its partners will know how to begin the restoration once the spill is stopped and damage can be evaluated , Moorman said .
Oil in the marshlands could destroy the root system of the Louisiana marsh plants and turn the areas into open water . Oil could impact millions of migratory birds that rely on marshland resources for the winter . Oil hurts birds by covering their plumage , poisoning their food supply and damaging reproduction . Experts should know more of what to do for the plants and birds once the oil is stopped .