Wildlife and mines can be found in abundance at the Kopaki Rit Nature Reserve

KOPACEVO, Croatia (CNN) -- A historic nature preserve is under threat from the remnants of the war that broke out after Croatia declared independence from Yugoslavia in 1991.

Croatia's Kopacki Rit Nature Reserve is home to rare birds, marshes and lush vegetation. But it also is dotted with leftovers from the war, including bunkers, trenches and deadly land mines.

"During the war, Kopacki Rit was on the front line, so the troops were in both sides and part of the troops were in the wetlands. Some of the parts are heavily mined, and those mines are still causing problems," said Tibor Mikuska, a biologist.

The 42,000-acre park is covered in lush vegetation and is home to 285 bird species, including rare varieties such as the black stork.

The war affected several animal populations, such as that of the red deer, which was hunted heavily. Nearly 7,000 lived in the park before the war but only about 1,000 remain. Many were killed, while others simply moved to safer surroundings.

The park, however, has survived for centuries. It was first given special status in the 17th century by Austro-Hungarian rulers.

During the war, the park was mostly controlled by minority Serbs who were rebelling against Croatian independence. Ethnic Hungarians and Croats were forced to flee the villages around the park.

Despite the war, the area is one of Europe's best preserved natural areas. It is bordered by the Danube and Drava rivers along Croatia's eastern border with Serbia.

Its wetlands, flooded for at least three months a year, are the biggest spawning ground for freshwater fish in the Danube.

Reuters contributed to this report.