Land Use History
Pittsburgh Botanic Garden is located on 460 acres of land with a long history of human intervention, including agriculture and industrial practices of resource extraction. Timber, gas and coal were harvested from the site in the last century, leaving the land degraded, habitats loss, and biodiversity reduced – until the Garden took over the land lease in 1997. In particular, restoring land heavily impacted by years of coal mining has been the primary focus of the land restoration efforts on the site.
Restoring the Land
The Pittsburgh Coal Seam is part of the Appalachian Basin coal region that was once a large inland swamp. During the Carboniferous Period (354 million – 290 million years ago), giant tree ferns and other plants flourished in this region. Over time, pressure and heat transformed the plant material into a high-carbon rock – coal. In the late nineteenth century and most of the twentieth century, coal was extracted from the Pittsburgh Coal Seam on land that became Pittsburgh Botanic Garden.
Depending on how close the coal seam is to the surface, miners use different removal strategies. Deep mining, specifically room-and-pillar mining, and surface mining both occurred extensively at the Garden’s site.
Abandoned Mine Land Restoration
Hazard Remediation
Mining for coal creates hazardous topographic features like Highwalls and Subsidence Pits. In 2018, the Garden began an extensive project to address these concerns. These areas were graded to create gentle slopes and sown with native seed mixtures to stabilize the soil and reduce erosion.
Reforestation
Following the science-based guidelines recommended by the Appalachian Regional Reforestation Initiative, the remined area was graded to create long furrows for planting. Horticulture & Conservation staff worked with hundreds of volunteers to plant 35 native tree species. Species were selected to achieve a mixed forest composition similar to the pre-industrial forest that existed at the site. A total of 14,500 seedlings were planted between 2019 and 2020.
Building Gardens
Land remediation, as exemplified by the Exhibit Garden project, accomplished both conservation and aesthetic goals: create a large bowl-shaped landscape feature; retain and enhance a naturally occurring pond; keep resources on site and build soil; and plant native species for increased diversity. Since most of the 6-acre site had to be cleared of vegetation prior to regrading, the Garden decided to retain the majority of the plant biomass on the property and use it to build new soil for future gardens.
Water Restoration
One of the first environmental challenges at Pittsburgh Botanic Garden was the presence of acid mine drainage (AMD). When air and water come into contact with exposed sulfurous rocks in coal mines, the water becomes acidified and is often contaminated with toxic dissolved metals. AMD is a persistent problem as the acidification process continues long after mines are abandoned and polluted water flows to streams and rivers.
At the Garden, AMD occurred at multiple points where mine drainage reached the surface. At one location, a limestone bed was installed underground next to the pond. Water is then redirected to the limestone tank where it is neutralized and returned to the pond. This stabilized ecosystem allows plant life to flourish, fish and other wildlife to quickly return, and ultimately the Lotus Pond was established. This project was awarded the 2014 Governor’s Award for Environmental Excellence and is an example of effective public-private partnerships generating tangible positive impact on the environment.
