Researching background for articles in this issue provides a cautionary tale about how difficult it is to predict what the future will bring.

In December 1991, the issue of air pollution and the Bay made the cover of the Bay Journal for the first of many times over the years, and air deposition had only recently been identified as a significant contributor of nitrogen to the Chesapeake.

"New studies of emissions in the region indicate that growth in the two main sources of nitrogen oxide (NOx) emissions — motor vehicles and fossil-fuel power plants — will cancel pollution reductions required by the 1990 amendments to the Clean Air Act," I reported.

One of the studies cited, from the Maryland Department of the Environment, found that in a best case scenario, NOx emissions might be reduced 5 percent by 2010 — and then only if vehicle travel didn't increase after 2000.

The outlook was so bleak that the Bay Program declared air pollution to be "uncontrollable." The 40 percent nutrient reduction goal in place at the time wasn't applied to sources considered uncontrollable (which, at the time, also included nutrients from New York, West Virginia and Delaware).

Today, the amount of nitrogen deposition landing on the Bay watershed from NOx emissions has declined 55 percent. Emissions from utilities nationwide have declined about 70 percent, and total emissions from motor vehicles are being reduced even as people drive more than ever.

Far from being uncontrollable, the nitrogen reductions from air pollution are being counted toward cleanup goals — and are responsible for about a third of the reductions achieved since 1985, according to computer model estimates.

The air reductions were driven by a long string of regulations that forced NOx emissions to be reduced from just about every possible source. Some are still in the works: The EPA is to release new rules for gasoline formulations and motor vehicle emissions later this year. Of course, it also helped that air reductions were driven by science showing the need to curb pollution to protect human health.

Other predictions also went awry, but with less positive outcomes.

In June of that year, I reported about the opening of the new $12 million fish lift at the Conowingo Dam, the first of four that would be completed on hydroelectric dams on the river in the next decade to help get American shad to suitable spawning grounds.

A deputy secretary of the U.S. Department of Interior predicted that the entire river would be open to shad migration by 2000, and it would boost the upstream sports fishery by $42 million to $185 million annually.

While all of the fish lifts did get completed by 2000, few American shad are using them. Last year, just 22,143 actually passed Conowingo, and only 224 made it past all four dams on the river — far short of the numbers envisioned.

Shad have suffered from multiple factors, including the biological and technical difficulties involved with getting fish past four dams, and the overarching problem that the coastwide shad population appears to be at record lows, so there are fewer fish to pass.

Now, agency biologists and utility officials are trying to identify the next steps for Conowingo (See "Dam relicensing acknowledges that with power comes responsibility," on page 10).

Awesome ospreys

Bay Journal copy/design editor and Bay Buddies/Chesapeake Challenge author Kathleen Gaskell is among the throngs who have become addicted to observing the daily antics of Tom & Audrey, the osprey parents who can be observed on the Chesapeake Conservancy's Ospreycam at www.chesapeakeconservancy.org/Osprey-Cam. If you haven't checked out the cam yet, there's still time to see the eggs hatch and young osprey learn to fly. In the meantime, can test your osprey knowledge by checking out this months Chesapeake Challenge and Bay Buddies quizzes on page 26.