by Melinda Beam
Under the Endangered Species Act, the northern spotted owl (strix occidentalis caurina) was categorized as a vulnerable species in 1990. The United States Fish and Wildlife Service (USFWS) concluded that the birds are in danger of extinction, citing loss of old-growth surroundings as the primary threat.
Several experts have blamed timber harvests and a lack of forest growth for the owls’ decline, and forest conservation remains paramount in order to preserve their habitats.
Federal agencies including USFWS have found a decline in nesting sites due to the major loss of evergreen trees which owl populations need in order to thrive. Only around 1,700 pairs of spotted owls remain in the Pacific Northwest.
Subspecies of the spotted owl like the great horned owl, barred owl, flammulated owl, western screech owl, eastern screech owl, snowy owl, northern hawk owl, northern Pygmy owl, and the burrowing owl all share the same incredible white markings. For centuries, the white-spotted, dark brown, and northern spotted owls could be found throughout old-growth forests in the Pacific Northwest.
These dense forests provided the necessary protection for owls to relatively easily determine a perfect nesting location. Even with a bounty of eligible nesting sites, these monogamous organisms do not reproduce often and have a low juvenile survival rate. When loggers came onto the scene in the late 1800s, decimating around 80 percent of old-growth forests from Northern California to British Columbia, the spotted owl began to disappear along with the forests.
The logging industry has cut down over 15 billion board feet per year across the Pacific Northwest since World War II. This has led to habitat fragmentation, where one large area is divided up into smaller areas, causing isolation between species.
When nature-enthusiasts and environmentalists began to notice large sections of dense forest being replaced by clear-cuts in the 1980s, they began to form protests in big cities and take direct action in forests, bringing national publicity to the controversy.
Why Northern Spotted Owls are Endangered
As previously mentioned, the barred owl has recently been recognized as the primary threat to the northern spotted owl. Historically, the barred owl was native to eastern North America; however, the owl is quickly invading the northern spotted owl territory. The first appearance of the barred owl was in British Columbia in 1943. It was later found in Washington in 1965, Oregon in 1974 and California in 1981.
The barred owl has a higher reproduction rate and larger population than the spotted owl. The non-native is also larger and more aggressive than the spotted owl, giving it an advantage when resources are scarce. Following DNA sequencing of the northern spotted owl, the California Academy of Sciences’ first animal genome has been a congregated hybridization of the northern spotted owl and the barred owl.
In collaboration with the University of California Berkeley (UC Berkeley), University of California San Francisco (UCSF), the National Museum of Natural History in Paris, and the Howard Hughes Medical Institute, scientists extensively mapped the bird’s genetic material to better understand how this threatened forest dweller is interacting with non-native owls invading its habitat.
The two species have been producing offspring with one another since the 1980s. Hybrids have been found to display physical and vocal attributes of both owl species.
In Oregon, the northern spotted owl’s gene flow has been restricted by the dry, low-elevation valleys of the Cascade and Olympic mountains, but facilitated by the Oregon Coast Range. Due to population bottlenecks, there has been a decrease in genetic diversity and population size, as well as inbreeding.
In a study conducted by Funk et al., findings revealed the presence of population bottlenecks believed to be caused by the presence of barred owls and habitat loss. Due to the bottleneck, loss of an effective population size or the number of organisms producing offspring for future generations, a decrease in genetic variation is a possible threat to the spotted owl.
As populations decrease, the likelihood of inbreeding increases, lowering the success rate of reproduction and survival. Due to less variability and mutations in the genes, the spotted owl will continue to lose its adaptability as inbreeding increases. This finding also reveals that conservation will have to go beyond protecting areas and controlling non-native species in order to maintain a sustainable spotted owl population.
As genetic diversity of the spotted owl strix occidentalis continues to decline and the effects of climate change continue to worsen, the risk of disease among owls will also likely increase. As climate change occurs, areas that were once cooler are becoming warmer, allowing an increase in vector-borne diseases to spread to these areas. Although it is only speculation, scientists believe the spotted owl could be susceptible to certain parasitic diseases, such as West Nile Virus.
The barred owl is also less susceptible to disease than the northern spotted owl. In a study conducted by Ishak et al., the spotted owl was found to have a substantially higher number of blood parasite infections in comparison to the barred owl, suggesting the presence of a compromised immune system.
Additionally, as the barred owl has moved into the spotted owl’s habitat, there is a high likelihood that barred owl diseases will also move into the spotted owl’s territory. As the encroachment of the barred owl and the effects of climate change continue to pose a threat to the spotted owl, human intervention might be the only way to save them.
Pacific Northwest Forestry
The Northwest Forest Plan
As an indicator species, when northern spotted owl populations are abundant, forests retain diversity. As the spotted owl disappears, the diversity and health of forests rapidly decline. The owls’ biotic and abiotic features collectively form ecosystems that provide an array of services to humans and their environment, including the prevention of floods, landslides, and soil erosion. The owls’ presence also leads to improvements in nutrient-dense soil, salmon fisheries, water quality, and greenhouse gas reduction.
Many environmentalists have been quick to stand up for the spotted owl as its population began to drastically decrease.
The spotted owl was placed on the Endangered Species Act as “threatened” in 1990, and the following year, a federal order to stop logging in spotted owl territory was granted until a plan was in place for total ecosystem conservation.
Meanwhile, “save a logger, eat an owl” became a popular phrase among loggers and those in support of the trade. By preserving the habitat of the owl over logging companies, private and state lands were under pressure for their timber, and fears concerning job loss increased.
The conservationists’ fear of losing the wilderness and its inhabitants was pitted against the loggers’ fear of losing their livelihood, which created an atmosphere of animosity.
As tension grew, president Bill Clinton sought to alleviate tension by holding a Northwest Forest Summit in Portland, which brought environmentalists, timber representatives, scientists, fishermen, and local officials together.
This summit led to the emergence of the Northwest Forest Plan. The plan guaranteed timber yields of approximately 1.1 billion board feet per year in Washington, Oregon, and Northern California public forests, which was an 80% decrease from previous yields. But the plan never fulfilled this promise, and was unsuccessful overall for timber sales. The plan did, however, prove to be successful for owl conservation.
Conservationists saw this not only as a win for the owl but also for the forest ecosystem. Little did they know that they had also triumphed over climate change. In a 2016 study conducted at Dartmouth, clear-cutting was found to stir up and loosen stored carbon in the soil. This elevates the risk of carbon returning to the atmosphere as carbon dioxide, playing a role in climate change along with the loss of trees.
Yet, even with the logging companies at bay, the northern spotted owl population continues to decline at an average rate of 3.7% per year. Forest fires often eliminate old-growth forests, which is one reason why loggers argue the importance of cutting trees in these areas. But the spotted owl faces an even larger enemy.
The primary cause of their decline is now believed to be the emergence of the non-native barred owl species. With the discovery that the barred owl was the primary threat to the spotted owl, new conservation strategies were essential for the species’ survival.
In 2011, the USFWS made revisions to their plan for the northern spotted owl, recommending that the areas of the spotted owl’s residual habitat should be protected. The primary focus on protecting federal lands remains, but for a full recovery, additional areas will likely need protection.
The USFWS plans to control barred owl populations in hopes that the two species can coexist. Additionally, they suggest the use of “experimental removal” of barred owls in conflicting areas to see if it might have a positive effect on the spotted owl. As a third recommendation, the USFWS suggests the use of active management to regenerate forest ecosystems that will hopefully work to combat climate change, natural disasters, and disease.
This new plan comes with recommendations, whereas the former held regulations. Pressure previously placed on logging companies has significantly diminished since the focus has shifted to the barred owl. Old-growth forest conversation is still incredibly important, and timber companies are in the process of reviewing practices that may have adverse effects on flora and fauna.
However, there are no concrete plans for conservation–only recommendations, studies, and protocols have been provided.
No incentives were provided for logging companies to stop cutting down old-growth trees, and environmentalists fear that conservation of the spotted owl and old-growth forests may not continue. This plan was also released before the deadline, neglecting to utilize the extra time to seek further public opinion.