The quick and direct answer is the easiest to understand, but often the hardest to give. I find this to be especially true when discussing plant population trends. It’s extremely tempting to draw conclusions about what is happening in an area after collecting only a year or two of data, but this is dangerous! Populations undergo natural annual variation, something that is especially apparent in Colorado this year. We’ve been returning to many of our permanent monitoring plots around the state, checking out how different rare plant species have been reacting to the extraordinarily low moisture levels this summer. Generally, the plants, like many common species, have been struggling. If we looked only at the number of individuals in some of our plots last year (a very wet year) vs. this year, we might be tempted to conclude that the populations were declining dramatically. Luckily, we have more data than that for many of the species. Looking back at previous years’ data, it becomes clear that the number of individuals in a plot has tended to fluctuate up and down the entire time the team has been monitoring.
I really noticed this distinction last week when we traveled to northern Colorado to monitor Phacelia formosula. At the first plot we visited, the plants looked great! It was the first plot of anything I’d seen this year that looked noticeably better than it did last year. There were many plants, and the majority of them were in flower. With excitement building, we moved on to our next plot. Alas, there were almost no plants here! The third and final plot seemed to take the middle road, with approximately the same number of plants we had seen the year before. Looking at these three plots it was obvious that populations fluctuate, and not always in the same way as their neighbors just a small distance away. We left with another year’s worth of data, secure in the knowledge that several years down the road we may be able to notice meaningful trends.
BLM Colorado State Office