A hummingbird flew into New York’s Times Square Friday, and has been hovering and flitting high over the heads of tourists and workers ever since.

Never mind that the bird arrived via jumbo screen — the arresting image was intended to turn attention to humanity's tenuous place in nature. The onscreen message: “Earth Overshoot Day is August 1…Because We Have Only One Earth…#MoveTheDate.”

Created by the Global Footprint Network environmental nonprofit, Earth Overshoot Day estimates the point in the year when humanity has consumed more natural resources and created more waste than Earth can replace or safely absorb in a year. The Aug. 1 date projected this year is earlier than any time in the dozen years the calculation has been made and a warning, especially, of the heightened challenge from the accumulation of greenhouse gases.

“Fires are raging in the Western United States. On the other side of the world, residents in Cape Town have had to slash water consumption in half since 2015,” said Mathis Wackernagel, CEO of the Oakland, California-based Global Footprint Network. “There are consequences of busting the ecological budget of our one and only planet.”

The electronic billboard campaign in Times Square — with additional images of a blooming hibiscus from renowned slow-motion nature filmmaker Louie Schwartzberg — will be followed by a YouTube and Facebook livestream July 31 and Aug. 1. The live video feed will feature environmental leaders from around the world, including representatives from the United Nations, the World Wildlife Fund, Earth Day Network and others.

The Earth Overshoot concept is designed to bring urgency to climate issues that can seem distant in time and place. It aims to keep citizens and decision-makers in touch with spiraling carbon dioxide levels, particularly Americans who don’t live in coastal flood zones or in the path of more frequent and sizable hurricanes.

How Earth Overshoot Day is calculated

When the first overshoot calculation was announced in 2006, it found that Earth used a year's worth of resources by Oct. 9. The Global Footprint Network determines the date by drawing data from the United Nations, the International Energy Agency and the Intergovernmental Panel on Climate Change, among others. These estimates of productive land and sea area, grazing land, cropland and fishing grounds are expressed in so-called global hectares. This measurement (roughly 2.5 acres) is meant to be a standard unit, projecting average productivity, that can be tallied to represent the Earth’s total "biocapacity."

The researchers then examine the demand side: mankind’s need for crops, livestock and fish, timber and space for urban development, along with a calculation of the forests’ capacity to absorb carbon dioxide emissions from the burning of fossil fuels. The difference between this “ecological footprint” and the Earth’s biocapacity represents the overshoot.

The Aug. 1 date declared this year means that, for the final five months of the year, mankind is overdrawing natural resources. Framed another way, it would take 1.7 Earths to supply the resources needed to feed, clothe and sustain Earth's 7.6 billion people for a year.

Global Footprint Network also calculates the biocapacity and ecological footprint at the national level, offering a look at how much each country is living beyond its home-grown resources. It shows, for example, that the United States has a biocapacity of 3.6 hectares per person but that the average consumption is 8.4 hectares per person, meaning that Americans are running a 4.8 hectare per-capita deficit. Stretched across a population of 317 million, that country uses all of its native resources by March 15, the formulation suggests. To continue consuming at current levels indefinitely, the U.S. would need the resources of five Earths.

That's in sharp contrast to nations that have little industry and relatively few cars and trucks and often substantial forests, pumping oxygen back into the biosphere. So Suriname in the northern end of South America, has a biocapacity of 97 hetacres per person, but each of its 496,000 inhabitants only uses 2.7 hectares, on average, annually. So the tiny nation produces a large 94.6 hectares of "reserve." Because the construct is only theoretical, though, Suriname can't escape the excess carbon dioxide most other countries pump into the atmosphere. And it exports surpluses of wood and commodities that other countries can't produce on their own.

Andrew Simms, a progressive British political economist who helped conceive the idea, said it is important to show how cultures live beyond their own resources. “The wealthiest countries, in particular, depend on a much larger land base than they have themselves to enjoy the material lifestyles they are accustomed to," Simms said. Wackernagel said his group uses the statistics conservatively and that, if anything, the overshoot date underestimates humanity’s impact on the planet.

A global response

The calculation is not without critics. A World Wildlife Fund official in Britain wrote a column in 2010 calling the footprint “clever” and “succinct.” But he added that the diverse array of data it compiled — from greenhouse gas emissions, to rainforest destruction, to corn yields — was hard to reconcile and made the calculation “a useful guide stick rather than anything absolute.”

Rush Limbaugh offered a less generous critique after the announcement of the overshoot date in 2015. “If we have exhausted our yearly allotment of natural resources," Limbaugh asked, "then why are we still breathing?”

Wackernagel responds that just because resources like water and oxygen remain available, it doesn’t mean they aren’t being depleted to threatening levels. “We can live off of depletion for a time,” he said, “but not forever.”