Mark's career has been focused on protecting and restoring important natural, wildlife, recreational and cultural resource lands. He worked with the Iowa Natural Heritage Foundation from 1980 to 1994. The Foundation has been involved in protecting over 140,000 acres of Iowa's wild places, including the conversion of 800 miles of former railroads to trails and conservation corridors. Mark was one of the founders of the Land Trust Alliance (the national association of land trusts) and served as chair for three years. He was instrumental in creating the ten-state Mississippi River Trail, Inc. which is creating a trail the length of the Mississippi River. Mark also helped create the Resource Enhancement and Protection Program in Iowa which provides $15-20 million annually for conservation and recreation, the State Recreation Trail Fund which provides $1-2 million annually and co-lead the effort in 2010 to create the constitutionally protected Iowa Natural Resources and Outdoor Recreation Trust Fund to be funded by future sales tax proceeds.

Mark has taught three years at the Conservation Finance Camp at the Yale School of Business and Environment. Mark has also been a regular presenter on local funding initiatives at the National Land Conservation Rally of the Land Trust Alliance. He has been involved in numerous successful project campaigns as well as two county referendums and a state constitutional amendment campaign.