The butterflies did not die from disease, poison or predator; they died of exposure.
It was cold that night, but no records were set. The temperatures were nothing the butterflies hadn't experienced in the past, since they have come to this place for countless centuries.
The fatal difference that night, according to scientists, was the trees - or lack of them. Excessive logging had decimated the area. The forest had been thinned and fragmented. Without dense stands of timber to serve as a kind of thermal blanket that moderates extremes in temperature, the butterflies could not - and mostly did not - survive.
The afflicted colonies have rebounded but not recovered. Today, there are fewer monarchs in the mountains of central Mexico. The clouds of butterflies that once rose in the warming sun, creating a sound tourists and researchers described as a roaring wind, doesn't happen as often anymore.
There are fewer trees as well due to the unabated logging. If nothing changes, researchers said, the forests and the butterflies will probably vanish within the next few decades. The environmental consequences of their extinction are not known; however, biologists said it would be felt throughout much of western North America.
Popular conservation tends to be all about the animals: the panda, the tiger, the condor and even the monarch butterfly. These creatures are the iconic faces of the conservation movement. They are the reason millions of Americans donate billions of dollars each year to groups promoting environmental and animal welfare causes.
Being warm and fuzzy or a symbol of nature's majesty only counts for so much, said Bill Toone, a conservation veteran who has organized and participated in dozens of programs and projects worldwide.
Toone said it is more important to address the human condition. Good intentions and money alone, for example, won't save the monarch if people continue to illegally decimate the forests for firewood and profit.
"We in conservation are making an enormous mistake," he said. "Perhaps it wasn't a mistake 20 years ago; however, today with more than 6 billion people in the world and resources stretched thin, we're trying to convince needy people that they should save the animals first.
"But humans are animals, too, and animals look first to their own interests, to the survival of themselves and to their offspring. For the vast majority of the world, that still means getting enough food, clean water and good shelter. Until those problems are addressed, it's hard to really and effectively save things like butterflies, habitat or natural resources."
So Toone, with a handful of like-minded advocates, launched the Escondido, Calif.-based ECO-LIFE Foundation three years ago. The foundation's goal is to address some of the human problems that underlie and influence conservation: poverty among indigenous peoples, lack of clean water, poor shelter and inadequate food.
Toone said until these needs are addressed, many conservation efforts, even those well-funded and well-advertised, may be nothing more than a delaying action.
Toone, 51, speaks from experience. He has worked in Africa, the Americas and Asia. He helped develop and operate the San Diego Zoo's California condor recovery program, a much-lauded program that exemplifies what happens when conservation runs into human roadblocks.
In 1987, the last remaining condors in the American wild were captured and taken to zoos for captive breeding. It was a controversial move, but proponents said it was necessary: The species was on the verge of extinction, only 22 birds remained.
Now, there are 289 birds, with 138 individuals released into remote areas of California, Arizona and Mexico.
"The breeding and management successes of the captive program have been outstanding," said Toone, who remains a conservation specialist for the Zoological Society of San Diego.
Condor success in the wild world, however, has not come as readily. The U.S. Fish and Wildlife Service estimates that $35 million to $40 million has been spent on condor recovery programs over the past two decades. After more than 15 years of releases, only five condor chicks have fledged in the wild. During the same period, at least 67 birds died in the field and 15 others were recaptured and returned to captivity.
Condors in the wild face many challenges, almost all human-caused. Chief among them is lead poisoning, which causes mental impairment, disables their digestive systems and renders them weak and vulnerable to predators. It's the leading cause of wild condor deaths.
The contamination comes from bullet-laced carrion killed by hunters and consumed by scavenging condors. A University of California Davis study estimates more than 30,000 such carcasses are left in the field each year.
"The condor food supply is almost completely contaminated,"Noel Snyder, a retired biologist with the Fish and Wildlife Service, told the journal Environmental Science & Technology.
Toone said efforts to reduce lead poisoning through hunter education programs are helpful but likely won't solve the problem. It may require dramatic action, such as banning lead ammunition.
A similar dilemma confronts Mexico's monarchs. There you can't see the butterflies for the lack of trees and you can't see the trees due to the lack of protection.
"The butterfly reserve is twice protected by presidential decree," said Toone, who has been conducting monarch butterfly research for almost two decades. "Unfortunately, it is safer for the poorly armed (government) officers to hassle old women for dropping trash than to face the well-organized, well-funded and well-armed illegal loggers."
The Mexican police aren't the real or only problem, said Toone. Rather, it's a fundamental question of economics and need.
"Most of the overwintering sites occur on ejido land - land owned by the indigenous who, like the American Indians, have and enjoy a greater or lesser degree of independence from the federal government," Toone said. "Sadly, the indigenous people share in few benefits afforded to others in Mexico. In general, they are poorly schooled and have few opportunities to improve on their education. In this area, they are primarily subsistence farmers. Some estimates say that up to 80,000 trees per year are used simply in cooking and staying warm."
In their first foreign field project, Toone and ECO-LIFE are trying to help in two ways. A Web site has been developed to promote education and communication among indigenous conservation groups, residents and law enforcement.
"There's a lot of confusion there about what's going on. The police say they don't know where the loggers are. The people don't believe the police. We're trying to bring some transparency by establishing a Web site and system where complaints and solutions can be posted by communities, organizations and the press."
ECO-LIFE is trying to reduce the amount of timber cut by locals for cooking and heating by helping them install more fuel-efficient concrete and mud stoves.
"Each stove costs about $150 once all costs are figured," Toone said. "We work through various nonprofits in Mexico to build them. It's a way of providing work during the low season (when there are few tourists and no butterflies). We prefer not to give the stoves away and suggest either a financial contribution toward their construction or assistance to other groups involved in planting trees, monitoring the forests or maintaining facilities."
The foundation has distributed more than 200 stoves and hasplans to distribute 700 or more in the next few years.
These are small efforts and Toone is the first to admit the situation is complex. It requires the work of many groups and agencies doing a variety of things.
What sets ECO-LIFE's work apart from other programs, Toone said, is its immediacy and quick return on investment. Toone believes that's critical for the butterflies and the people as well.
"We can be quite certain that the overwintering butterflies will disappear (if things don't change) before the last of the forest and the forest remnant will soon follow," he said.
"Forget about the butterflies and other wildlife; what will (the local people and) their children do then? How will they earn an income? Who will feed their babies? Will they be comfortable looking to the Mexican government for support? Or will they immigrate like so many millions of others to the streets and shantytowns of unfamiliar cities and countries to try and survive - often far from home?
"The management of these forests is much more than simply a wildlife conservation story; it is about entire communities of people very much dependent, as we all are, on wildlife resources."
Two years ago, in a much-debated article published in Worldwatch magazine, conservationist Mac Chapin wrote that "big conservation" - represented by organizations such as the World Wildlife Fund, Conservation International and The Nature Conservancy - was increasingly ignoring the needs and demands of indigenous peoples living in the lands these organizations were trying to protect.
Robert H. Nelson, a professor of public affairs at the University of Maryland, calls it "environmental colonialism" - the imposition of contemporary Western conservation practices upon native populations regardless of the effect on these populations or whether these practices are worthwhile. "It's obvious that in Africa, or any poor country, the long-run future of the wildlife and the environment will be closely tied to the solution of social, economic and political problems in the country, such as clean water," Nelson said.
"This is a problem for environmental groups, however, because they cannot easily raise money on that line of appeal, and they also have no particular skills in wider development issues. Rather than fold their tent, environmental groups - the American ones anyway - often turn to things like the national park model that basically tries to isolate certain environments from the rest of the country."
It's similar to trying to save Africa from the Africans, Nelson said.
The criticism has not gone unnoticed by the major conservation groups. Toone said there are now numerous examples of significant conservation collaborations.
"The challenge here is not so much to collaborate well with other conservation groups, but to draw new players into the circle from the development and humanitarian side of programs."
It does no long-term good, Toone said, if a donated $40,000 water pump fails and the locals don't know how to fix it. It makes no sense to build housing that is impractical and inconsistent with Third World realities.
Toone would like ECO-LIFE to be a collaborator. This means meeting needs and filling in gaps overlooked or not addressed by other aid groups.
"We're not a threat - and I certainly don't want to be perceived as one - to other conservation groups," Toone said. "We want to collaborate with others, do things they can't, fill a niche."
"The two words that describe Bill and ECO-LIFE are creativity and passion," said Jordi Honey-Roses, a former World Wildlife Fund biologist who met Toone while working in Mexico. "Bill's willing to take on unique projects that other organizations are not. Larger organizations are limited by conventional donors who are risk-averse. ECO-LIFE can get around this, and push the limits as to what conservation projects can look like."
At the moment, ECO-LIFE's list of accomplishments is relatively modest. The organization divides its focus between domestic and foreign projects.
In San Diego County, it consists primarily of education programs promoting water conservation. Much of the education is targeted at children and emphasizes the close relationships between wildlife and clean water.
"In the United States, conservation has largely alienated people. We are made to feel guilty for our standard and style of living," Toone said. "Conservation is seen as our way of doing penance. It shouldn't be that way."
The monarch butterfly program is ECO-LIFE's only current foreign project. Although, Toone said, there are plans to develop simple water collection and storage programs that can be used in remote parts of Mexico, Central America and Africa.
Toone practices what he preaches. His Escondido home is rigged to allow moisture collecting on his tile roof to funnel into underground tanks. The water is then used to sustain his gardens and trees. He estimates that in a single year he collects more than 23,000 gallons of water - and doesn't pay a penny for it.
"We all need to view resources as a good thing, something to use but to also save and use again and again," he said.
Years of conservation work, some of it painful, have taught Toone that humanity is inexorable. The future will only bring more people and more pressures upon what remains of the natural world.
Toone doesn't pretend to believe that conservation can prevail if it is seen as coming at too high a price.
"If you ask (struggling) people to sacrifice, to save wildlife," said Toone, "it's a losing battle."
Rather, struggling people have to see and understand that conservation is not just the right thing to do; it is a sensible thing to do as well. If they don't, every species suffers - including humans.