Sometimes good wine happens by accident or luck. Sometimes it’s inspiration. ­John Forrest of New Zealand’s Forrest wines has had both.

First, the luck. Back in 1996, Forrest noticed that a few rows of grapes were showing signs of bird damage earlier than usual, so he directed his crews to string bird netting along the vines. Not long afterward, the grape clusters developed signs of rot. Forrest realized that the netting had been used the previous year to protect grapes harvested late for his dessert wine, an unctuously sweet Riesling made from grapes shriveled by botrytis — the “noble rot” that, when properly controlled, can concentrate the fruit’s juices and flavors.

“It was a simple matter of the last netting [that went] into the barn the year before being the first taken out and used the next year,” Forrest, a gregarious, bearish New Zealander, recalled on a recent visit to Washington. The nets evidently had harbored botrytis spores and induced the rot on the next vintage. So he decided to keep that netting separate and use it each year for the dessert wine to help induce botrytis, which is a tricky proposition even in fair-weather years. Except in unusually rainy vintages, he has been successful.

Today, Forrest produces a reliably delicious dessert wine called Botrytised Riesling, and he credits at least part of his success each year to his accidental discovery and a few early birds that visited his vineyard.

The inspiration came several years later. Forrest, a former molecular biologist who switched to winegrowing in 1988 but never abandoned his scientific curiosity, attended a viticulture forum in Germany where a professor from Geisenheim, Germany’s top viticulture school, was discussing the effects of climate change on grapes. Average sugar levels had increased over two decades, the speaker said, leading to higher alcohol levels, while other characteristics that contribute to flavor had remained the same. In other words, Germany’s wines were getting more powerful but not tastier.

As grapes ripen, the speaker said, a certain part of the vine canopy contributes to higher sugar levels. So some effects of climate change could be counteracted, he said, by removing specific leaves from the vine in the weeks leading to harvest.

Climate change isn’t a problem for New Zealand grapes, Forrest said, but he sensed there was a market for refreshing wines with lower alcohol. He had experimented in the winery with various techniques to reduce alcohol but always thought the resulting wines lacked character. And like many other growers, he had practiced leaf pulling as a way to improve air flow and sunlight exposure in the vines. Now he was eager to see whether he could use the technique to create something new by reducing alcohol levels naturally, in the vineyard. 

So he began experimenting with strategic leaf pulling about six weeks before harvest — what would be late July or early August here in the Northern Hemisphere. The result was the Doctor’s Sauvignon Blanc, which features the racy, grassy qualities of Marlborough wines with only 9.5 percent alcohol, about 25 percent less than average. The wine may not have the richness and body of Forrest’s regular sauvignon blanc, but it is unmistakably New Zealand savvy.

“It’s a great wine for sitting on the patio on a hot summer day,” Forrest says. I agree.

Forrest says he could see this technique being useful in hot years when sugar levels could spike in chardonnay or pinot noir. The New Zealand government has funded research on the technique by other growers.

In addition to meeting a perceived market demand for wines with moderate alcohol levels, Forrest says, the technique has the potential to help other wine regions where climate change is affecting vintages.

“You know where this could really make a difference?” he asked me, his eyes wide as grape clusters. “Napa!”

McIntyre blogs at On Twitter: @dmwine.