shield是什么意思？

The treaty banning mining here, shielding 116 coveted ( ' , 令人垂涎的) reserves of iron ore, coal and chromium, comes up for review in 2048.

More than a century has passed since explorers raced to plant their flags at the bottom of the world, and for decades to come this continent is supposed to be protected as a scientific preserve, shielded from intrusions like military activities and mining.

Obama's successes seemed to act as a shield against this.