Understanding biome-level response to climate change

This month’s Scientific American contains a great article (“Arctic Plants Feel the Heat“) on how scientists are documenting climate change in the Arctic. Focusing on the two dominant biomes of this region, the tundra and the taiga, author Matthew Sturm explains how three sources of data are allowing us to see recent changes linked to global warming. Tree rings, which provide historical accounts of growth trends, have been used to show that many areas of the taiga have slowed in growth despite higher levels of carbon dioxide and longer growing seasons, probably due to drier conditions during the summer. Comparison of present-day photos with a rich serendipitously-discovered Navy photo archive of the arctic shows that the tundra is becoming shrubbier, supporting larger plants that can now survive the slightly-less-harsh winters. Using NDVI data from satellites, these twin effects of forest browning and tundra greening can be seen on a larger scale. The article contains a number of really vivid images showing these changes.

Beyond laying out the evidence, Strum does a great job of explaining two other key concepts: feedbacks and uncertainty. Using his own work on increasing shrub cover to illustrate these concepts, Sturm discusses how warming can accelerate due to changes in albedo, snow cover, and local interactions between plants. He also points out that the long-term effects of these changes are hard to predict in complex ecosystems, because we rarely have clear estimates of how positive and negative feedbacks will balance out.

This year I will be assigning this article to my Ecology students.