The Border Security, Economic Opportunity and Immigration Modernization Act of 2013, popularly known as the Senate "Gang of Eight" bill, may show a lot of promise for those seeking meaningful reforms in immigration and border policy. In fact, in a major departure from our usual neutrality on all things immigration, Sierra Club has come out in favor of a just path to citizenship for the 11 million undocumented Americans currently living in the shadows.

However, to avoid more environmental damage and environmental catastrophes, the "Gang of Eight" bill needs improvement.

The bill requires $1.5 billion in additional border walls. The Secure Fence Act of 2006 has taught us that when Congress forces Homeland Security to build walls, bad things happen - and they don't work.

Approximately 650 miles of border walls and barriers have already been built. Locations for many of them were determined by D.C. politicians thousands of miles away from these fragile borderlands. The walls don't stop people from crossing. They do, however, cause serious floods, damage natural habitat, block wildlife corridors and cost taxpayers billions of dollars to build and maintain.

New walls will only cause more environmental damage. Their construction and maintenance will drain our national coffers and distract Homeland Security from its mission.

Part of the reason existing border walls are so destructive is that many hundreds of miles were built without regard for the rule of law. The Bush administration used a waiver authority to dismiss 37 federal laws that protect wildlife, historic sites, public health, farmland, Native American graves and religious freedom.

The new bill expands that waiver authority, allowing it to be used for any border infrastructure, not just walls and roads. Border Patrol bases, towering security cameras, miles of high-voltage stadium lights, all could be built without regard for the rule of law.

Homeland Security's mission is not to breach the rule of law on the border, but to enforce it.

Some of the security provisions in the bill will probably have a positive effect at the border and the path to citizenship will help to address one of the root causes of migration across the border.

One hopeful example is the call for an additional 3,500 Customs and Border Protection agents. If this extra personnel is assigned to our official crossing points in border cities and towns, they could help decrease wait times, facilitate cross-border trade and stimulate the economy. More customs agents would also enhance border security more than additional Border Patrol agents, because most of the contraband entering the U.S. from Mexico is smuggled through official border crossing points.

There are also provisions to provide more training for Border Patrol agents on civil rights and environmental sensitivity.

As written, this bill poses serious challenges and threats to our borderlands. But it is also an opportunity: With a few small changes, we can abandon a failed policy of mindless wall construction, and restore the rule of law on the border.

Dan Millis, is program coordinator for Sierra Club Borderlands and an Arizona native.