November 11, 2019
Birds and Bases
Posted by: Emily Engle
Daniel Pauly stated, “An animal that is very abundant, before it gets extinct, it becomes rare. So you don't lose abundant animals. You always lose rare animals. Therefore, they're not perceived as a big loss.” This past month the journal Science published findings that north American bird species assemblages have lost approximately 3 billion birds since 1970, a 29% decrease in the last 50 years. In 1997 Daniel Pauly recorded the Shifting Baselines theory; a phenomena to which the world played witness but was blissfully unaware. The concept: as new generations of researchers further science’s understanding of the world, they measure changes in the context of “stock size[s] and species composition[s] that occurred at the beginning of their careers”; baselines which neglect to assess change over larger temporal scales. Although we may see gradual, seemingly minute variations over a short study period; our base starting point could be drastically different (or significantly lower) than those before us. This can result in massive differences when viewed as a whole as described in Rosenberg et al. (2019)’s findings. Initially developed in the context of modeling fisheries, Pauly’s theory is reflected in avian fauna’s recent population declines. It is these drops which precede rarity, foreshadow extinctions, and hold drastic implications for north American ecosystems, economics, and society. In the wake of Little St. Simons hosting a summit on avian conservation this past month, it is imperative we understand how to best combat measured assemblage declines.
Bird species function as indicators: they reflect the general health of environmental systems on which they depend and of which they are a part of. The net loss of 2.5 billion individual birds paints a grim picture for the integrity of ecosystems across North America. This decline has occurred through 12 families of birds, with at least 19 of our most common land birds experiencing the loss of over 50 million individuals. The paper acknowledges its estimates are inherently conservative. Declines are measured only within breeding populations; the loss of breeders may have much more drastic impacts considering their reduced reproductive output. As Pauly stated, “we don’t lose abundant species, only rare species”; we are witnessing the rarefication of once abundant birds and the decline in the health of their associated ecosystems across the continent. Birds function as predators and prey, and directly or indirectly influence species’ interactions within an environment. Fewer individual birds means fewer ecosystems operating in their entirety.
Avian fauna declines harbor implications for communities which depend on them and their ecosystems. Birds’ provide free ecological services to humans as pollinators, seed dispersers, provisions, and pest controllers; aids which greatly benefit modern society. However, in the wake of avian population declines, we will have to attempt to artificially replicate these practices and increasingly face the financial burden of their absence. Additionally, the U.S. has $49 billion dollar industry revolving around recreation such as bird watching. The shift in base assemblage populations will inevitably translate to an economic loss in addition to the loss of individual’s intrinsic value.
Conservation targeting species preservation neglects to protect the integrity of ecosystems as a whole. Going forward we should be striving to preserve regions of ecological importance to ensure habitat is available for surviving populations. North America is in the midst of “a long-developing but overlooked biodiversity crisis.” Rosenberg et al. (2019) call for targeted conservation action to protect bird species from decline. That said, Little St. Simons is of hemispheric importance for migrating bird species; the conservation of this landscape is helping to preserve key environments in the midst of widespread habitat loss across the country. Preserving populations, habitats, and their critical interdependence will help mitigate the realities of shifting baselines.
Today, almost one third of the U.S.’s species are at risk of extinction; translating to a potential loss of 8,500 different types of plants and animals according to Bruce Stein, the National Wildlife Federation’s associate vice president of conservation. Further, less than 20 percent of the country’s proximately 200,000 identified species have been evaluated for extinction threats; thus, “the true total of imperiled plants and animals is most likely much higher” (National Wildlife Federation). We are living the reality of shifting baselines: Our parents walked through landscapes which differed drastically from our own. On our current trajectory our great grandchildren will seldom see sparrows building mud huts under eves, or hear black birds calling through the marsh grasses. They will not experience the world and its wonders as we do. Without our intervention, they will only know a muted version of nature; a future which encompasses deteriorated environments, increased species’ rarity, and fewer individual animals given the reality of shifting baselines.
Interested in the North American Avian Declines?
To learn more about birds’ role in in the North American Economy, take a gander at U.S. Fish and Wildlife’s 2016 survey of Hunting Fishing, and Wildlife-Associated Recreation: https://wsfrprograms.fws.gov/Subpages/NationalSurvey/nat_survey2016.pdf
Curious to learn more about Daniel Pauly’s theory on shifting baselines? Check out his TED talk presentation:
* Header photo/graphic by Jillian Ditner from the Autumn 2019 Living Bird issue covering Rosenberg et al. 2019