TODAY | April 26, 2014
>>> four years now after the bp oil spill , there is still an impact that lingers. crude oil pumped into the gulf of mexico for 87 days, you may recall, when the deepwater horizon oil platform exploded, damaging what was already a delicate ecosystem. wildlife advocates say the effects are still being felt. the weather channel 's dave malkopf has the story.
>> reporter: four years after the bp oil spill disaster --
>> hundreds and hundreds of nets here.
>> reporter: director with the national wildlife federation took us 20 miles into the marsh where that black tar choked the life out of what was once a baby pelican nursery.
>> it's sad and sickening to watch the loss of a place like this.
>> reporter: as recently as last year, there were pelicans here. now just dead sticks.
>> you had anywhere from 25 to 30 feet of thick tar.
>> reporter: four years on, the tar is a problem. it's the oily sheen nobody ever cleaned up. so what you're seeing now is the effects of it moving up the food chain that's predictable from what we know about past spills. the sheen was absorbed by tiny bacteria.
>> the real question is what are the long-term effects.
>> reporter: wildlife officials worry it could be working its way into dolphins and other large predators.
>> still seeing increased numbers of dead dolphins coming ashore.
>> reporter: it's true a number of things may be killing dolphins along the gulf coast . scientists and lawyers are still trying to work out the oil's exact environmental impact here. bp says they've already spent $14 billion in clean-up efforts and the company heads back to trial early next year for damages. since the spill, many animal habitats here simply eroded away.
>> those areas.
>> reporter: used to be a land bridge here, islands around here. now they don't exist.
>> they don't exist.
>> reporter: just one mile north and you'll find some good news. state bird of louisiana is thriving, their eggs ready to hatch next month. despite losing their old home to the oil spill .
>> they're going to move where they have to move. it's just that we're running out of places for them to go to.
>> reporter: for "today," dave malkopf, at the mouth of the mississippi river in louisiana.