Donnell Brown and another cowboy move a grouping of bulls from one pen to another on rib-eye ultrasound day in March at the R.A Brown Ranch. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

A line of fire turns brown grass into black earth. Dan Charles/NPR hide caption

itoggle caption Dan Charles/NPR

A tall, rubbery weed with golden flowers Dalmatian toadflax is encroaching on grasslands in 32 U.S. states. pverdonk/Flickr hide caption

itoggle caption pverdonk/Flickr