If the science of ecology has demonstrated anything at all, it is this: No act thuds into isolation or oblivion. Everything is interwoven and responsive, with all natural processes intimately linked in a precisely balanced global ecosystem.

Each species, each creature, each organ, each cell, is finely attuned and adapted to its natural environment, and yet each one has its significant role in creating the precise environmental conditions for the next cell, the next organ, the next creature, and the biosphere as a whole.

The natural balance of ecosystems is so very finely tuned that a small change in just one component, be it the ozone layer, dioxin levels, tropical rain forest acreage, or blue whale survival, can make a tremendous impact, directly or indirectly, on seemingly unrelated systems even halfway across the world.

A classic example is the story of the formerly popular insecticide DDT. A minute amount got into water and was absorbed by filter feeding, tiny shrimp. These were eaten by small fish, which in turn were eaten by larger fish. Predatory birds such as osprey, eagles, or pelicans ate the fish, and — as the world was surprised to hear in the late 1960’s — the birds failed to reproduce because of DDT sprayed on mosquitoes hundreds of miles away.

The problem was that at every link in this food chain, DDT was becoming about ten times more concentrated in the animals. So, what started as parts per million in water ended up as deadly percentages in bird egg shells.

Then, of course, are the all-too-frequent environmental catastrophes precipitated by relatively tiny human misdeeds, such as oceanic oil spills, Chernobyl, and so on.

A more positive phenomenon is the environmental movement, where surprisingly small numbers of optimistic activists have managed to galvanize and redirect companies, industrial sectors, and even whole societies to recycle, conserve natural resources, and reduce waste and pollution.

In just a few decades, the environmental movement has become literally and figuratively a grassroots movement, and politicians worldwide are greening up. As the maxim goes, “Where the people lead, the leaders will follow.” In the last few years we have seen the UN Bruntland Commission on sustainable development, the Montreal accords on greenhouse gases, and the Brazil summit, where in each case close to 100 national leaders achieved consensus on major global environmental problems and what needs to be done to remedy them.

All of this has been accomplished on one single, simple premise. Each and every small private activity is essential to restoring the world’s natural environments to a healthy state.

The concept of “Think global, act local” neither begins nor ends with the environmental movement. It has been in the Torah for thousands of years.

Over 800 years ago the great Maimonides wrote in his Mishneh Torah:

Therefore every person should continuously regard himself as though he were equally balanced between merit and guilt. So, too, the entire world is half deserving and half guilty. If he makes one wrong move, he tips the scale for himself and for the entire world to the side of guilt and causes destruction for himself. When he obeys one Commandment, he weighs himself and the entire world to the side of merit, thereby saving himself and the world from harm (Mishneh Torah, Hilkhot Tshuva 3:4).

Historically, such statements were taken on faith alone. In previous generations, no one could really see or understand how this vast world could possibly respond to the small local deeds of a single person.

It is only in our generation that this principle has become a practical and evident reality in our daily lives. Planet Earth has become one global village where the part can instantly affect the whole, not only through global ecology, but also through global communication, global economics and global politics.

The bottom line in both natural science and Torah life is that in all human deeds, speech, and even thought, one is free to choose among alternative paths leading to personal failure and ecological disaster (G-d forbid) on one hand, or personal success and global well-being on the other.