The Sixth Extinction — Maya Lin's What Is Missing?

Source: Decline of the Empire

I found out yesterday that Vietnam Memorial artist Maya Lin will be giving a public lecture here in Pittsburgh this coming Friday. I also learned that she had produced a series of short films called What Is Missing? to call attention to the ongoing mass extinction of plants and animals on Earth. This human-caused extinction is called The Sixth Extinction to group it with the other “Big Five” extinctions that have occurred on Earth during the Phanerozoic Eon (543 million years to the present).

The study Are we in the midst of the sixth mass extinction? A view from the world of amphibians provides some background on those previous mass extinctions and analyzes the alarmingly high rate of amphibian extinctions in the present. Another recent paper (Nature, March 3, 2011) asked Has the Earth’s sixth mass extinction already arrived?

Palaeontologists characterize mass extinctions as times when the Earth loses more than three-quarters of its species in a geologically short interval, as has happened only five times in the past 540 million years or so. Biologists now suggest that a sixth mass extinction may be under way, given the known species losses over the past few centuries and millennia. Here we review how differences between fossil and modern data and the addition of recently available palaeontological information influence our understanding of the current extinction crisis. Our results confirm that current extinction rates are higher than would be expected from the fossil record, highlighting the need for effective conservation measures.

[My note: A 75% species extinction rate sets a very high bar. If only 66% of vertebrates go extinct in the next 500 years (or even 100 years), could we hold our heads high and say we averted a mass extinction? I dont think so.]

I’ve included Figure 2 and the provocative text below it to spur discussion of the endangered status of  life on Earth. After that I’ve posted the first and second videos from Maya Lin’s What Is Missing? I will post again on this subject later this week, postponing my own remarks until then.

Another approach is simply to ask whether it is likely that extinction rates could have been as high in many past 500-year intervals as they have been in the most recent 500 years. Where adequate data exist, as is the case for our mammal example, the answer is clearly no…

A second hypothetical approach asks how many more years it would take for current extinction rates to produce species losses equivalent to Big Five magnitudes.

The answer is that if all ‘threatened’ species became extinct within a century, and that rate then continued unabated, terrestrial amphibian, bird and mammal extinction would reach Big Five magnitudes in 240 to 540 years (241.7 years for amphibians, 536.6 years for birds, 334.4 years for mammals). Reptiles have so few of their species assessed that they are not included in this calculation.

If extinction were limited to ‘critically endangered’ species over the next century and those extinction rates continued, the time until 75% of species were lost per group would be 890 years for amphibians, 2,265 years for birds and 1,519 years for mammals.

For scenarios that project extinction of ‘threatened’ or ‘critically endangered’ species over 500 years instead of a century, mass extinction magnitudes would be reached in about 1,200 to 2,690 years for the ‘threatened’ scenario (1,209 years for amphibians, 2,683 years for birds and 1,672 years for mammals) or,4,450 to 11,330 years for the ‘critically endangered’ scenario (4,452 years for amphibians, 11,326 years for birds and 7,593 years for mammals).

This emphasizes that current extinction rates are higher than those that caused Big Five extinctions in geological time; they could be severe enough to carry extinction magnitudes to theBig Five benchmark in as little as three centuries…

From the What is Missing? Foundation on Vimeo.

Read more at Decline of the Empire