Immigration Control and Biodiversity in North America

By Stuart H. Hurlbert
Published in The Social Contract
Volume 21, Number 3 (Spring 2011)
Issue theme: "How political correctness corrupts environmental science"


In July 2008, the editors of Frontiers in Ecology and the Environment invited me to submit an 800-word essay that responded to the question: Are increased attempts to control immigration from Mexico (including building fences and increasing militarization of the border) likely to have a net positive, negative, or neutral effect on biodiversity in the U.S. and Mexico? An introduction to and brief literature review on the topic was prepared by Lori Hidinger (2009) as background. This is the draft of my essay that was accepted by Frontiers Associate Editor Peter Mooreside; I have modified it by giving it a title and by expanding by a few lines my quote from Hardin’s essay. The politics surrounding later rejection of this essay by Frontiers Editor Sue Silver are detailed in Hurlbert (2011)

Lori’s question takes two complex issues — immigration and protection of biodiversity — and tries to guide us to a focused discussion by posing a question that considers only U.S. and Mexican biodiversity and, implicitly, illegal immigration only “from Mexico.” [Actually, it was never made clear whether the question was drafted by Hidinger or Frontiers editors. S.H.]

Biodiversity in both countries would benefit

An answer must be predicated on many assumptions, but my short one is that a great reduction in illegal immigration will have positive effects on biodiversity in both Mexico and the U.S. Additional benefits to biodiversity will accrue to both countries if rates of legal immigration were also cut back to moderate levels, say 100,000-300,000 per year in contrast to ca. 1,000,000 in recent years.

The reasons are simple. A growing human population — and all that implies for wildland destruction, resource consumption and waste generation — is the single greatest threat to biodiversity and other environmental values. In the U.S. mean family size (“total fertility rate”) dropped to about 1.8 children per woman more than three decades ago. If the U.S. had not allowed greatly increased legal and illegal immigration starting in the 1960s, we could have achieved U.S. population stabilization by now.

As it is, continued high immigration rates and large family sizes of predominantly poor and uneducated people from Mexico and Central America have raised mean U.S. family size now to 2.1 children, and it continues to increase.

For Mexico the biodiversity question is more complicated. Education and family planning programs have been successful in getting mean family size down to 2.4 in that country, and its rate of population growth to about 1.1 percent per year. Export to the U.S. of many of its poorer citizens has contributed to the reduction of both Mexico’s mean family size and its rate of population growth, just as it has increased these for the U.S.

Halting illegal immigration from Mexico to the U.S. and reducing the annual quota for Mexican legal immigrants (and those from other countries) would serve as a wake-up call for Mexico to take stronger measures to lower its population growth rate. Benefits to biodiversity in Mexico would follow.

Habitat and wildlife issues along the border

No question about it, construction of border fences to impede illegal immigration, as well as vegetation-destroying, trash-dumping behavior of the illegal immigrants themselves, causes environmental damage in some locations to particular habitats and species. Lori does a good job of introducing the literature on that.

Unfortunately the environmental organizations and scientists who have raised the biggest ruckus about damage caused by border fences have been a bit disingenuous and narrow in their focus, thus losing some credibility with other scientists and the general public. They have focused too exclusively on environmental impacts of border fences, and been silent on the much greater but spatially more diffused environmental damage resulting from illegal immigration’s contribution to U.S. population growth. Illegal immigrants and visa overstayers just since the 1960s, for example, plus their descendants, may now number somewhere on the order of 30 to 60 million, i.e., 10-20 percent of the U.S. population. These additional tens of millions in our population have a collective negative impact on biodiversity and other environmental values that is orders of magnitude greater than any impacts that will ever be caused by border fences.

An ethical and philosophical choice

A core issue in debates about environment-population connections is whether action — for the very few willing to actually act — should be based on a globalist or an internationalist ethic. The distinction is discussed at length by Beck and Kolankiewicz (2000). The internationalist ethic is that sovereign nation-states are to be respected, that they will work together but in their own self-interests, and that self-interests should include assisting the success of other nations. The globalist ethic favors the “elimination of the sovereign nation-state as a locus of community, loyalty, economy, laws, culture and language” (Beck and Kolankiewicz 2000) and large transfers of national power and responsibilities to international bodies, such as the World Court, European Union, United Nations, and so on.

Garrett Hardin (1989) pointed out why, pragmatically and ethically, an internationalist philosophy is likely to be the most successful one for dealing with the overpopulation problem. He suggested,

[N]ever globalize a problem if it can possibly be solved locally.…We will make no progress with population problems, which are a root cause of both hunger and poverty, until we deglobalize them.… We are not faced with a single global population problem but, rather, with about 180 [now 200+] separate national population problems. All population controls must be applied locally; local governments are the agents best prepared to choose local means. Means must fit local traditions. For one nation to attempt to impose its ethical principles on another is to violate national sovereignty and endanger international peace. The only legitimate demand that nations can make on one another is this: “Don’t try to solve your population problem by exporting your excess people to us.” All nations should take this position, and most do.

I have criticized the “globalist copout” in harder language, making special reference to the Ecological Society of America, Green Party, and Sierra Club (Hurlbert 2000). Such organizations take, implicitly or explicitly, the position that overpopulation is a global problem, and that an individual nation with a high level of immigration may not or should not reduce those levels in its own interests. They prefer that immigration issues be kept out of their publications, meetings, platforms, policy statements, and political action alerts. That is why when the U.S. Senate passed a bill (SB2611) in May 2006 that would have roughly doubled the rate of U.S. population growth by massively increasing immigration rates, no mainline environmental organization or scientific society opposed it or even notified their members about it, let alone pointed out the environmentally disastrous consequences it would generate. Fortunately, the bill was killed by wiser heads in the House of Representatives and an uprising of literally hundreds of thousands of ordinary voters more alert than the scientific and environmental communities. 


Beck, R., and L. Kolankiewicz. 2000. The environmental movement’s retreat from advocating U.S. population stabilization (1970-1998): A first draft of history. Journal of Policy History 12:123-156.

Hardin, G. 1989. There is no global population problem. The Humanist 49(4):11-13, 32.

Hidinger, L. 2009. To fence or not to fence. Frontiers in Ecology and the Environment 7:350-351.

Hurlbert, S.H. 2000. The Globalist Copout. The Social Contract 10:193-194.

Hurlbert, S.H. 2011. ESA, Frontiers, immigration, and political censorship. The Social Contract (this issue).

About the author

Stuart H. Hurlbert is an emeritus professor of biology at San Diego State University and is currently secretary of Californians for Population Stabilization.

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