Now that people are comparing the ongoing Aliso Canyon natural gas leak to the seemingly endless Deepwater Horizon oil spill that fouled Gulf shorelines in 2010, it is well past time to take a look at how this leak might be affecting birds. The leak has been spewing gas since Oct. 23, and is still weeks away from being stopped.

On the one hand, the answer is easy. The Aliso Canyon leak – also known as the Porter Ranch leak, for a nearby residential development – is producing massive amounts of global greenhouse gas emissions, which recent research shows stands to have a devastating long-term effect on birds. But the immediate effects on birds are less clear.

California Gov. Jerry Brown declared a State of Emergency around the leak earlier this month. Southern California Gas, which operates the Aliso Canyon storage facility, which is the source of the leak, has been forced to relocate hundreds of residents who claim that the gas – and additives that make it detectible by smell – are affecting their health.

Bird experts have noted that several important species make use of the Porter Ranch area, including breeding Grasshopper Sparrows and endangered Coastal California Gnatcatcher. But lack of regular data is making it hard to discern clear effects from the gas leak.

According to Jim Moore, who compiles the annual San Fernando Valley Christmas Bird Count, the most recent count held in December in those areas near the leak show fewer numbers of birds. For instance, the 2015 count in nearby Lime Kiln resulted in 55 individual birds of 15 species, while the 2012 Lime Kiln count showed 471 individual birds and 34 species.

But Moore is quick to point out that the leak is not the only factor that could be reducing the number of birds observed. He notes that the larger San Fernando Valley circle is also showing steady declines, going back well before the leak, and in areas that are unaffected by the leak. For instance, the total number of birds observed on the larger San Fernando Valley Christmas Bird Count was 14,594 in 2013, 12,247 in 2014, and 9991 in 2015.

“What you’re really seeing here is the impact of the drought,” said Moore.

San Fernando Valley Audubon Society’s Mark Osokow, adds that development is also a growing factor in this part of Southern California. His chapter recently appealed a decision allowing a nearby development to move forward.

“The reasons for our vehement opposition go beyond a simple desire to slow the out-of-control growth that Los Angeles continues to experience, taking wildlife habitat with it,” said Osokow, who linked the proposed development to the gas storage facility. “Additional adverse impacts include outright destruction of the habitat — and public enjoyment — provided by more than 400 oak trees, damage to the surrounding riparian and upland landscape, disruption of existing wildlife corridors, degradation of two perennial tributaries of the Los Angeles River (Browns and Mormon creeks), increased erosion, interference with public access, a new major road fragmenting some of the finest remaining open space in the area, and the re-grading of an estimated 7.5 million yards of soil in a seismically unstable area.”

This last week, a Los Angeles county supervisor called for a moratorium on annexations to the City of Los Angeles to support new development near the Aliso Canyon gas storage facility until the cause of the leak can be investigated. The Hidden Creek development is likely to be halted as part of this effort.

The National Audubon Society last year completed a seven-year study which found that global warming threatens the survival of 170 California species in the coming decades. This includes iconic California birds such as the Brown Pelican, Allen’s Hummingbird, Yellow-billed Magpie, and many others.

The California Air Resources Board estimates that the Aliso Canyon leak has emitted the equivalent of 2.1 million metric tons of carbon dioxide. This is more greenhouse gas than 440,000 cars emit in a year. A recent article in the Los Angeles Times looks more closely at what that means for climate change.