Les: The article states: "The relatively large number of calves born last year exacerbated the problem. The youngest and weakest animals are often the first to die in harsh conditions like these, according to the Institute."
High offspring rates means that the feeding the previous year was good. So there was plenty of food then. MAybe caused by warmer weather and CO2 that grows more food for grazing. There may not have been enough grazing areas the following year which is natural for whitetail deer here in the US as well. What happens is over a number of good years, the herds expand tremendously. Hunting doesn't deplete them enough. Then, the deer suffer deaths with a 50% reduction in one bad winter because the deer can't get to the food or there's not enough to go around. But this is normal. It doesn;t mean we're have another ice age.
Likewise, are the scientists jumping to conclusions about the reindeer? Similar things could be happening there from time to time. Populations expand and contract, yes, especially due to changes in the environment and weather. So what?
Also, I'd like to know how many deer expanded because the higher CO2 and warmth gave them better grazing in the good years. The greater population would have set them up for a bad year this year. Did the scientists investigate that aspect?