An accidental nature preserve
The Korean Demilitarized Zone (DMZ) is a 250-kilometer long and roughly 4-kilometer wide strip of land created by the 1953 armistice that ended the Korean War. This buffer zone is one of the most heavily fortified borders in the world, strewn with landmines and military installations. This near-total exclusion of human activity for over 70 years has turned the DMZ into an involuntary park. Damaged forests have regrown, and agricultural lands have returned to a natural state.
The landscape holds countless craters from artillery shells and bombs. Over the decades, these scars of war filled with rainwater, transforming into hundreds of small, isolated ponds. Each crater became a separate freshwater habitat, a tiny island ecosystem. This isolation is the cause. Organisms that found their way into these ponds—likely invertebrates like insects and crustaceans carried by wind or birds—were cut off from other populations. Each pond developed its own unique environmental conditions, led to rapid, small-scale evolution. These accidental wetlands are now considered valuable bioreserves.
The DMZ's unique biodiversity
Surveys conducted by South Korea's National Institute of Ecology have documented nearly 6,200 species within the DMZ. The zone is home to 102 of the Korean peninsula's 267 endangered species. This means about 38% of the country's threatened species live in this narrow strip of land. The diverse terrain includes mountains, wetlands, lakes, and tidal marshes, supporting many types of life.
The crater ponds specifically contribute to this biodiversity. They are habitats for 417 species of benthic macroinvertebrates—organisms that live at the bottom of a body of water. While specific studies on new invertebrate species in the DMZ craters are not widely published due to the area's inaccessibility, similar environments show how this happens. A study of World War II bomb craters in Hungary found they provided an important habitat for 274 species, including a rare endemic shrimp. The DMZ craters, undisturbed for even longer, offer a similar natural laboratory. The larger DMZ ecosystem is a sanctuary for mammals like the Asiatic black bear, Siberian musk deer, and the long-tailed goral. It also is an important wintering habitat for seven of the world's 15 crane species, including the endangered red-crowned and white-naped cranes.