Here's a breakdown:

Natural:

* Geological Formation: The Great Plains were formed over millions of years by geological processes like tectonic uplift, erosion, and sedimentation.

* Climate and Vegetation: The Great Plains are characterized by their semi-arid climate, grasslands, and diverse ecosystems. These are natural features.

Manmade Impact:

* Agriculture: The Great Plains are a major agricultural region. Large-scale farming, including the use of irrigation and industrial agriculture, has significantly altered the landscape and ecosystems.

* Urban Development: Cities and towns have sprung up across the region, altering the natural landscape and wildlife habitats.

* Infrastructure: Roads, railways, and pipelines have been built, fragmenting natural habitats and impacting wildlife movement.

* Water Management: Dams, reservoirs, and irrigation systems have altered water flow and impacted native ecosystems.

Conclusion:

While the Great Plains are a natural geological feature, their current state is heavily influenced by human activities. The region's landscape, ecosystems, and resources are constantly shaped by the interaction between natural processes and human actions.