Semi-natural ecosystem:

“an ecosystem which has been altered by human actions, but which retains significant native elements” (IUCN 2000). 

International Union for Conservation of Nature, Species Survival Commission, Invasive Species Specialist Group. 2000. IUCN guidelines for the prevention of biodiversity loss caused by alien invasive species. Approved by the 51st Meeting of the IUCN Council, Gland Switzerland, February 2000