Old vs. new wind turbines: a look at wildlife fatality

The Journal of Wildlife Management has published 3 studies looking at wind farms, their fatal impacts on birds and bats, and the effectiveness of different measures to deal with the problem. This is a particularly difficult issue because it represents a major conflict between two of the most important environmental concerns of our time - clean energy and biodiversity conservation. Given the importance of this topic, Conservation Maven is spotlighting two of these studies today (see Reducing bat mortality from wind turbines: testing new methods)

Can you reform a wind turbine? The case of the Altamont Pass...
The Altamont Pass Wind Resource Area in Northern California is a notorious example of an early wind power project that has inflicted a huge number of fatalities on many species of birds - a number of which are protected under state and federal laws. The facility, which began operations in the 1980's, was until recently the largest wind farm in the world with a permitted generating capacity of 580 megawatts.

The Altmont facility has undergone a couple of major changes over the years that have the potential to reduce impacts on birds and bats. From 2005-2007, regulators required that wind operators implement a Bird Protection Program that consisted of a variety measures such as relocating hazardous wind towers and shutting down during certain periods. Also, in 2005 wind operators replaced 126 older Flowind turbines with 31 much-taller Vestas. These new turbines were spaced farther apart and spun at lower speeds - traits that many felt would be better for birds.

Researchers Shawn Smallwood and Brian Karas looked at a decade's worth of data to figure out whether these measures have resulted in a reduction of fatalities for birds and bats in the Altamont wind facility. The researchers counted the number of bird and bat fatalities by species from 1998-2003 - i.e the period before any measures were implemented. They also determined the number of fatalities from 2005-2007, the two-year period that the mitigation measures were implemented. Finally, they measured fatalities for the new Vesta turbines. The study found the following:

Study Findings...
1) Bird deaths were very high from 1998-2003 totaling 14.2 /MW/ year and spread across a large number of species. Meanwhile bat deaths were very low (though the researchers caution that bat mortality is harder to measure because of quick scavenging of carcases and may be under counted).

2) Surprisingly, the rate of bird mortality was greater during the period of 2005-2007 by 85% for all raptors and 51% all birds. The researchers offer a number of possible explanations for these results including methodological bias. However, they speculate that the increase may have occurred because mitigation measures had unintended negative consequences. For example the researchers state:

"Wind companies left vacant lattice towers at ends of rows as flight diverters, but this practice may have caused more raptor fatalities because raptors readily perched on vacant towers, which were adjacent to operating turbines."

3) Lastly, the study found that the new Vesta turbines had a substantial decrease in bird fatalities (54% in all birds and 66% in raptors) compared to older models co-generating during the same time period. However bat mortalities increased by 800%.

The authors recommend that in order to reduce bird casualties in the area for management of the area the old-generation wind turbines should be carefully removed as soon as possible. This would reduce estimated annual fatalities 54% for all raptors and 65% for all birds, while adding about 1,000 GW-hours of wind energy annually due to the improved capacity of new-generation turbines. The researchers, however, concede that a downside to these changes might be an increase in bat mortality.

Source:	Journal of Wildlife Management
Title:	Avian and bat fatality rates at old-generation and repowered wind turbines in California
Authors:	Shawn Smallwood and Brian Karas