JUDY WOODRUFF: Time now for our weekly segment on science and technology, the Leading Edge.

And this week, Hari Sreenivasan is here with an update on a pair of important stories.

HARI SREENIVASAN: They are important findings and analyses on a pair of stories we have

long been covering, the health of bees and the impacts of climate change.

A recent study looked at the economic consequences of climate change and concluded it will make

the U.S. poorer and more unequal if present trends continue.

The South would be hit the hardest.

A different set of studies looked at the health of bees in connection to insecticides used

in crops.

Bees are critical for our global food production.

Honeybees alone are responsible for pollinating $15 billion of U.S. crops.

The new papers demonstrated the popular insecticide used in agriculture called neonicotinoids

can be harmful to bees.

Miles O'Brien is with us again.

Miles, we have been looking at or scientists have been thinking about the chemicals that

are used in insecticides as kind of one of the number one culprits for colony collapse

for a long time.

So, what is so new about these studies?

MILES O'BRIEN: Well, you're right, Hari.

There have been a lot of studies in the past looking at bees and these insecticides, which

are coated on the seeds and absorbed -- they call it systemic to the plants.

They have been widely used for a decade, an alternative to spraying insecticides on the

plant as they grow.

The concern is that they can harm pollinators.

But, so far, that's only been a theory in the lab.

Separate teams in Europe and Canada tested the possible link between these neonics and

bee losses in the field for the first time.

They placed bee colonies close to crops that had been treated with the neonicotinoids and

other colonies far away from agriculture.

They sampled a variety of specimens, pollen, nectar, larvae, bees themselves, of course.

And they say the insecticide is not only found in the crops they are meant to protect, but

it spreads to other plants in the area that are attracted to bees, and it persists for

months.

HARI SREENIVASAN: So, how does it affect the bees, and what happens to the whole colony?

MILES O'BRIEN: That's the key question, connecting those dots.

Researchers at York University in Ontario did a second test in the laboratory mimicking

what they found in the field.

And they exposed bees to a small amount of the neonicotinoids-infused pollen.

And those bees stopped -- get this -- maintaining the hygiene of their hive.

Typically, bees will remove sick or dead bees.

But the insecticide-exposed bees for some reason stopped doing this, leaving sick bees

inside the hive.

And the beehive became a pigsty, if you will.

I caught up with Nadejda Tsvetkov, one of the lead authors of the York University study.

NADEJDA TSVETKOV, York University: What we found in our study was that worker bees from

exposed colonies die 23 percent sooner, so that's a very big hit to the colony.

They also had abnormal foraging behaviors.

We found also that the colonies had difficulty replacing a queen.

So, over time, we had more and more queenless colonies, which, unless there is an intervention,

the colonies will perish.

MILES O'BRIEN: At first blush, this study seems to put to rest the neonic collapse debate.

But, in a separate study also published last week, a European team found some bee colonies

in Germany that thrived even though they were close to fields with neonic-treated crops.

This led researchers to believe there must be other geographical or environmental factor

in play.

Maybe some bees are more susceptible to the toxins, depending on their locations, for

example.

In short, the studies suggests the effects of neonics on bees are inconsistent.

But that study was funded in part by the German chemical and pharmaceutical giant Bayer, which

happens to be the maker of neonicotinoids.

Now, in a statement, Bayer says it remains convinced that neonicotinoid seed treatments

have no short- or long-term negative effects on bees, and that these seed treatments are

useful and effective tool for farmers.

HARI SREENIVASAN: In the totally different category of climate science, there was a big

study this week.

And, usually, when climate studies come out, we're looking at environmental impacts.

What was interesting about this one was, it was looking at economic impacts.

Tell us a little bit about that.

MILES O'BRIEN: Well, this one is a very impressive study on climate change.

Scientists in the climate realm teamed up with economists, the dismal science meeting

climate science, if you will.

And they looked at the economic impacts of climate change as you project out to the future.

And perhaps the most interesting finding was that climate change will hit different socioeconomic

classes differently.

Here's Berkeley scientist and lead author of the study Solomon Hsiang.

SOLOMON HSIANG, University of California, Berkeley: In the South, where it's hot, and

along the coasts, we might see populations losing the equivalent of 20 percent of their

income, whereas, in the cooler Northern and Western regions, we actually see that populations

might benefit a little.

And because the North tends to be wealthier and the South tends to be poorer, what we

see is that, in the future, climate change is going to increase economic inequality within

the United States.

HARI SREENIVASAN: So, how does the U.S. fare overall?

MILES O'BRIEN: Well, the team estimates that for each degree Fahrenheit increase in global

temperatures, the U.S. economy overall loses about 0.7 percent of gross domestic product,

with each degree of warming costing more than the last as you go up.

So, the U.S. as a whole is not a winner economically.

HARI SREENIVASAN: So, does it break down by industry?

Say, for example, agriculture might be hit harder or real estate?

MILES O'BRIEN: Well, agriculture, especially in the Midwest, will likely suffer immensely.

That seems obvious.

But it could be comparable to the Dust Bowl of the 1930s, according to these researchers.

Of course, real estate on the coastline, that's another obvious one.

But here's a surprise.

The team found the biggest economic impact of climate change was in health care.

They expect people living in the South especially will be hit more with heat-related complications,

like heatstroke.

Managing that and dealing with the victims is, of course, very expensive.

HARI SREENIVASAN: And this is happening to a population that's already poorer than the

general average in the United States.

MILES O'BRIEN: And there is the vicious cycle.

HARI SREENIVASAN: All right.

Miles O'Brien, thanks so much.

MILES O'BRIEN: You're welcome, Hari.