Major Climate Change 5,200 Years Ago Could Repeat

An anonymous reader writes "The climate was altered suddenly some 5,200 years ago with severe impacts. Famouse glaciologist professor Lonnie Thompson have found clues that show history repeating itself. Thompson has spent his career trekking to the far corners of the world to find remote ice fields and then bring back cores drilled from their centers. Within those cores are the records of ancient climate from across the globe. He outlined his fears today at the annual meeting of the American Geophysical Union in San Francisco. 'The evidence clearly points back to this point in history and to some event that occurred. It also points to similar changes occurring in today's climate as well,' he said."

Comments

Bioaccumulation

[hey!]

Sure, and in WW2, recruits were doused with DDT powder to get rid of body lice, with no ill effect, as is agreed by anyone who knows anything about the subject.

The key is that the form in which a substance is delivered determines if it can be absorbed into the body and delivered to the right places to do damage. This is the same reason that the idea of spiking a water supply with plutonium to kill millions of people is not going to work.

DDT is not all that acutely toxic. But it can be delivered to animals, particularly predator birds, in a very harmful way.

The key is that DDT persists in the environment. It is not broken down by organisms ingesting it, it is mainly stored in their tissues. Thus it disappears from the environment very, very slowly. Exotic organic chemicals that behave this way, or that break down into other chemicals that behave this way, are a problem even if they don't necessarily have immediate impact on the environment. If critter A ingests the rather low concentrations in the general environment, no particular harm occurs. What people immediately missed is that if critter B eats critter A, he'll get a somewhat bigger dose of the material than critter A did, because terrestrial animals need to consume something like ten pounds of food to create a pound of body mass. Critter C gets an even bigger dose, all the way down to critter Z which gets a huge dose.

This process of amplification of the background concentration of a non-biodegradable substance is called bioaccumulation. Birds are particularly vulnerable because their energy requirements are so high, especially raptors like eagles.

Yet, even so, the effect of DDT on birds is not very acutely toxic. It has a subtle effect. Unfortunately that subtle effect happens to be that they lay eggs with extremely brittle shells.

Personally, I don't think DDT should have necessarily been banned, however, it was overused. It could have been used in emergency situations for a limited time at a rate close to the rate at which it would eventually disappear (if that rate could be determined). However it was used in typical 50s fashion as a miracle quick fix agent. The spirit is not completely lost -- we use antibacterial agents in soap, even matresses, for absolutely no good reason.

In any case, materials now in use, such as permethrin (targetting adult insects) do break down in the environment. This means that they don't bioaccumulate. The disadvantage is that you have to use them more frequently. The advantage is that you use them in response to an actual problem. Other materials such as BT that target larval stage insects not only biodegrade, but target smaller habitats. Rather than saturate broad swathsw environment with an agent that kills adult insects (including beneficials), you target the specific habitat where insects develop in their early larval stages. Furthermore with integrated pest management, a combination of strategies are used such as targetting and reducing specific habitats important to precise life stages of specific insects.

The bottom line is that properly and wisely applied, the world probably could make use DDT. But we were wrong to use it the way we did, and probably right to ban it so we'd be forced to develop effective and environmentally responsible strategies and materials. And we have. If we hadd DDT in our armamentarium, it'd only make a marginal difference.