By NICK PERRYCARTERTON, New Zealand (AP) â¿¿ Dairy farmer John Rose has sent more than 100 of his cows to the slaughterhouse over recent weeks as a severe drought browned pastures in New Zealand's normally verdant North Island. He had to thin his herd so the remaining 550 cows have enough to eat, and he's supplementing their diet with ground palm kernel as the grass in his fields withers. "We try and make sure they've got water and shade during the day and do the best we can for them," he said. "It's very hard to remember when the last rainfall was." The drought is costing farmers millions of dollars each day and is beginning to take a toll on New Zealand's economy. On Friday, the government officially declared its most widespread drought in at least 30 years. Parts of the North Island are drier than they've been in 70 years and some scientists say the unusual weather could be a harbinger of climate change. There has been little significant rainfall in the northern and eastern parts of the country since October. Still, some are finding the dry, sun soaked days a boon. Vintners call the conditions perfect. And city dwellers are reveling in eating lunch outdoors or spending evenings at the beach in a Southern Hemisphere summer that never seems to end. Farmers estimate the drought has so far cost them about 1 billion New Zealand dollars ($820 million) in lost export earnings with the damage rising daily as they reduce their herds, which in turn reduces milk production. Farming, and dairy cows in particular, drives the economy in the island nation of 4.5 million and the drought is expected to shave about a percentage point off economic growth. New Zealand's last significant drought was five years ago and also cost farmers billions of dollars.