The need to limit immigration follows when we combine a clear statement of our main environmental goals — living sustainably and sharing the landscape generously with other species.

At the current level of 1.5 million immigrants per year, America's population of 306 million is set to increase to over 700 million people by 2100. Recent proposals would increase immigration to over two million annually, which has the potential to nearly triple our population to over 850 million by the end of the century. Scaling back immigration to 200,000 per year would greatly reduce America's population growth. Environmentalists are losing the battle to create a sustainable society and protect wild nature.

Sprawl development destroys 2.2 million acres of wild lands and agricultural lands each year; over 1300 plant and animal species remain on the endangered species list, with more added each year; water shortages in the west and southeast are being used to justify new river- killing dams and reservoirs; and U.S. carbon emissions continue to rise.

There are arguments against reducing U.S. immigration that deserve consideration. In what follows, we analyze the arguments for the mass immigration status quo, or for even more expansive immigration policies. In the end, we find them unconvincing.

1. Immigration is now the main driver of U.S. population growth.

2. Population growth contributes to a host of environmental problems.

3. A growing population increases America's environmental footprint beyond our borders and our disproportionate role in stressing global environmental systems.

4. In order to seriously address environmental problems we must stop U.S. population growth.

5. We are morally obligated to address our environmental problems.

In 2006, the United States passed the 300 million mark in population — that's 95 million more people than were here for the first Earth Day in 1970 — with little comment from environmentalists.

In 2007, Congress debated the overhaul of immigration policy, now it looks likely to be set with no regard for its environmental consequences. We would like to see an immigration policy within the context of a commitment to sustainability. We don't believe that clean air and water; livable, uncrowded cities; sharing the land with the full complement of its native flora and fauna — are compatible with continued population growth.

From 1880 to the mid-1920s, America experienced an immigration boom, during which immigration averaged 600,000 annually. From 1925 to 1965, the US had an immigration policy, which allowed 200,000 people into the country annually, on average. The U.S. population grew during this time, from 115 million to 194 million, primarily due to high rates of natural increase.

By the 1970s, American women were averaging fewer babies and the US was well-positioned to transition from a growing to a stable population. Without post- 1970 immigration, the U.S. population would have leveled off below 250 million in the first few decades of this century. It didn't happen, because Congress greatly increased immigration levels. Between 1965 and 1990, immigration averaged one million people annually.

Since 1990, immigration has increased to approximately 1.5 million annually - one million legal and half a million illegal — the highest rate in history.

Between 1982 and 2001, the US converted 34 million acres of forest, cropland, and pasture to developed uses, an area the size of Illinois.

The number one cause of sprawl, by far: population growth. Between 1982 and 1997, 52% of sprawl was attributable to population increase, while 48% was attributable to misguided policies that increased land use per person.

Poor land use planning and bad transportation, zoning, and tax policies are important in generating sprawl.

Cities with growing populations sprawled even more.

Several states that managed to decrease their per capita land use during this period also sprawled, due to high rates of population growth. If we want to stop sprawl we must change the transportation, tax, zoning, and population policies that encourage it.

As the world's largest economy and historically largest greenhouse gas emitter, the US has a moral obligation to lead the world in meeting this challenge. A good start would be striving to stabilize greenhouse gas emissions. Meeting even a modest objective will prove difficult, if our population continues to grow.

The US CO2 emissions increased 20.4% between 1990 and 2005. We would have to decrease our emissions by 20.4% per person to get back to 1990 levels, at our current population. But if we double our population, we will have to decrease per capita emissions 58.5 percent to reduce CO2 emissions to 1990 levels. They are thus less likely to happen.

Re-engineering the world's largest economy and changing the consumption patterns of hundreds of millions of people are immense undertakings that will be difficult, expensive and only partly successful. Americans must reduce our per capita consumption of land and energy in order to meet these challenges. On the other hand, recent population growth has increased Americans' total land and energy consumption and made these problems even worse. Americans must address both overconsumption and overpopulation if we hope to create a sustainable society. U.S. population growth contributes seriously to both domestic and global environmental problems.

We propose: * Cut legal immigration to 200,000 per year. * Reduce illegal immigration by enforcing sanctions against employers who hire illegal workers. * Rework trade agreements, to help people live better lives in their own countries.

Political theorist Chandran Kukathas maintains that citizens of rich countries have no special claims to the resources and opportunities into which they have been born and that the Earth's resources be distributed as equally as possible, including allowing freedom of movement. He says to wealthy Americans: "You don't have to give up anything yourself to help poor people overseas live better lives. You can fulfill any moral obligations you may have toward them by allowing them to come here and cut your grass, cook your food, and diaper your children."

But with "open borders," the interests of nonhuman nature would be sacrificed completely to the interests of people. Human appropriation of natural landscapes has progressed so far in America that any further appropriation is unjust. Accepting a general right to immigrate leaves no room to take nature's interests seriously, in the United States or elsewhere, since it undermines any possibility of limiting the human appropriation of nature. For this reason alone, it must be rejected by anyone committed to generous sustainability.

People around the globe who live in poverty, insecurity, and injustice. Even the most generous immigration policies will not help most of them, since only a small percentage can conceivably emigrate from their home countries, and the worst off rarely have the resources to do so. The wealthy people of the world — including not just citizens of "the West," but hundreds of millions of people in the developing world — owe the world's poor people something. Not the lucky few millions who manage to immigrate to the West, but the billions who will have to sink or swim where they are.

The United States government should be much more generous and intelligent with development aid to poor countries It should fully fund international family planning efforts, which help both nature and the poor.

It should set trade policies to benefit poor workers and protect nature, rather than to maximize trade. The United States should pressure foreign governments to respect their citizens' rights, as mandated by international law. Individual Americans should support charities with effective international aid programs, such as Oxfam and the United Nations Children's Fund.

We should cultivate personal and professional friendships across borders, in an effort to understand and appreciate our fellow human beings.

One common argument says that we should focus on consumption, not population as the root cause of our environmental problems. "Don't buy big suburban houses; don't buy gas guzzlers; don't put air conditioners in those houses and cars. Americans' high level of consumption is the problem — not our population."

But as we have seen, it is Americans' overall consumption that determines our environment impact. Overall consumption equals per capita consumption multiplied by population. So if high consumption is a problem, population growth must be, too.

Others argue that immigrants consume less than the average American. Likely the immigrants increase their consumption the longer they live in the country. Immigrants come to this country to achieve "the American dream" and pass greater opportunities on to their children and grandchildren. Two million more immigrants this year may mean 10 million more Americans 100 years from now — and if history is any guide, those 10 million Americans will live pretty much like other Americans. The descendants of last century's Jewish and Italian immigrants do not seem to consume less than the average American today; there is no reason to think that the descendants of today's Mexican and Chinese immigrants will consume less than the average American 100 years from now. Bottom line: If American consumption levels are too high, the problem is only made worse by population growth.

Another argument made by many American environmentalists is that overpopulation is important, but that it is a global, not national issue that can only be solved through international action. No one argues: "Deforestation is a global problem, therefore we shouldn't worry about deforestation in our own country, or on the local landscape." Or: "Species loss is a global problem, therefore we should fund species protection efforts elsewhere, to the exclusion of efforts where we live." Those who care about deforestation or species extinction often work especially hard to prevent them in the places they know best, and are applauded for doing so. Besides, "global" efforts to halt deforestation and species loss are largely a summing up of local and national efforts focused on particular forests and species.

The "globalist" argument fails, because overpopulation occurs on a regional scale as well as on a global scale. For example, it is perfectly valid to say: "Nigeria is overpopulated; its population is so large and is growing so fast that it has trouble providing jobs for its young adults, or building sufficient water and sewer facilities for its cities." The people of Nigeria will have to live directly with their failure to correct overpopulation tendencies and they cannot wait for the world to solve all its problems before they act to solve their own.

Think globally, don't act locally" is terrible advice. It is possible and necessary to work on multiple levels at once.

Some argue that immigration just moves people around, so it is - or may be - environmentally neutral, or even benign. We plead guilty to a special concern for America's wildlife and wild lands. Environmentalism necessarily involves love, connection, and efforts to protect particular places. It involves acting as if they are the most important landscapes in the world and using our most accessible political levers to protect them. At a time when Americans move on average once every six years, arguing that we should further downplay our ties to particular places and communities is a bad idea.

Moving people to America, far from being environmentally benign or neutral, increases overall global resource consumption and pollution. This in turn threatens to weaken the already-stressed global ecosystem services that we all depend upon — with the world's poorest people facing the greatest danger from possible ecological failures.

America's permissive immigration policies appear to enable demographic and ecological irresponsibility and continuing social injustice. Consider Guatemala, where currently about 10% of the adult population lives and works in the United States. Guatemalan women's TFR averaged 4.6 children in 2005, for an annual growth rate of 2.4% per year. The Guatemalan government outlaws abortion - except when a mother's life is at risk - and does little to encourage contraception. Guatemala has high deforestation rates and an unjust, highly inequitable distribution of wealth. But there is little effort to change any of this, perhaps because the negative effects of local overpopulation are lessened through immigration and counterbalanced, for many individuals, by the positive incentives of having more remittances from family members in the United States.

Many pro-business proponents praise mass immigration above all for increasing economic growth. Immigration brings in poor unskilled workers willing to work physically demanding jobs for less money than native-born Americans, and highly trained professionals with the specialized skills needed by high-tech companies. Immigration creates more domestic consumers. Immigration also reduces the cost of many goods and services, and this too increases overall consumption. In all these ways, immigration results in "a bigger, more productive economy."

But Harvard economist George Borjas, says: "immigration induces a substantial redistribution of wealth, away from workers who compete with immigrants and toward employers and other users of immigrant services." Between 1980 and 1995, immigration increased the number of high school dropouts by 21% and the number of high school graduates by only 4%." During this same period, the wage disparity between these two groups increased 11%, with perhaps half of that disparity a result of mass immigration.Between 1980 and 2000, immigration reduced the average annual earnings of high school dropouts by 7.4%, or $1,800 on an average salary of $25,000.

While the economic effects of immigration are complex and the details are open to debate, it appears that over the past few decades high immigration levels have contributed to increased economic growth, lower wages for the poorest Americans, and an increase in economic inequality in the United States.

An immigration policy that benefits rich citizens - who hire immigrants - at the expense of poor citizens - who compete with them - seems prima facie unjust.

Second, accepting greater economic inequality in exchange for greater overall wealth seems a foolish trade-off for Americans today. We are already wealthy enough to provide for our real needs and reasonable desires. Further wealth when combined with greater inequality is a recipe for frustration, envy, and social tension.

Mass immigration's contribution to economic growth is the most important reason to oppose it. Human economic activity is the primary driver of ecological degradation. Future generations are going to have to reject the paradigm of an ever-growing economy and instead develop a sustainable economy that respects ecological limits. The sooner we get cracking on this, the better. Here in the United States, economic and demographic "growthism" are intimately intertwined — yet another reason why American environmentalists cannot ignore domestic population issues.