California's dwindling pastures

A group of tule elk graze on the lawn of a home on D Ranch in Point Reyes National Seashore, California, April 9, 2015.

A herd of tule elk leap over a fence in Point Reyes National Seashore, California, April 1, 2015. REUTERS/Robert Galbraith

Cattle graze in the pasture of D Ranch in Point Reyes National Seashore, California, April 9, 2015. REUTERS/Robert Galbraith

A sign is seen in Point Reyes National Seashore, California, April 1, 2015. REUTERS/Robert Galbraith

The Point Reyes National Seashore is one of the few parks in America with agricultural operations, some of them dating back to the 1800s. They were purchased by the federal government to create the preserve and the lands were leased back to the same families for agriculture. In the 1970s, tule elk were reintroduced to the park. REUTERS/Robert Galbraith

The seashore is the only national park with tule elk, which are not found outside California. REUTERS/Robert Galbraith

The state's tule elk population shrank by the 1800s to a handful of animals in southern California. As the population gradually rebounded, 10 elk were reintroduced in 1978 to the northern end of Point Reyes. REUTERS/Robert Galbraith

A cattle drinking pond is seen on a ranch in Point Reyes National Seashore, California, April 1, 2015. REUTERS/Robert Galbraith

In 1998 park workers transported 28 of the growing herd farther south. Those elk, which now number 212, split into two groups, including the 92 that migrated to grazing lands on three farms. REUTERS/Robert Galbraith

Tule elk and cattle graze together in the D Ranch pasture in Point Reyes National Seashore, California, April 9, 2015. REUTERS/Robert Galbraith

A herd of tule elk stand in a group at a fence line in Point Reyes National Seashore, California, April 1, 2015. REUTERS/Robert Galbraith

There are serious concerns, based on past experience, about erecting a giant fence. Point Reyes' northern herd has always been fenced off and its population dropped from 540 to 286 last year because, experts believe, old stock ponds the elk used for water dried up in the drought and left them to die of thirst. REUTERS/Robert Galbraith

Signs are posted along a highway near Point Reyes National Seashore, California, April 1, 2015. REUTERS/Robert Galbraith

A group of tule elk stand near a road in Point Reyes National Seashore, California, April 9, 2015. REUTERS/Robert Galbraith

A tule elk stands on a hillside in Point Reyes National Seashore, California, April 9, 2015. REUTERS/Robert Galbraith