How the geographic range characteristics of a species can affect its conservation

By Elana Rusnak, SRC intern

For many of us scientists, our end goal is conservation of our target species. But what does this mean, and how do we reach these goals? Unfortunately, the answer to this question is not cookie-cutter and requires the input of multiple factors that are not so easily or frequently studied.

At the largest scale, the two broad measurements of geographic range can either provide too much or too little area to be taken into account with regards to protecting a certain species: the extent of occurrence (EOO) and the area of occupancy (AOO). The area of occupancy is all the local area in which a species has been recorded, but only accounts for those localized areas. It may not take into consideration the other hospitable habitat in which individuals simply haven’t been recorded yet. The extent of occurrence is generally larger; as it encompasses all of the area a species could possibly live in, including the space between the recorded individuals (Gaston, 1991). The debate between area of occupancy and extent of occurrence may yield different results, which could cause complications especially with policymakers. While it may seem ideal to cover as much habitat as possible in order to protect a species, it is expensive and requires a lot of enforcement, therefore making it difficult for policymakers to go only on extent of occurrence, since it might include habitat in which the species does not ever reside. However, it also might include area in which a species is migrating, but only during a small part of the year. Why would they want to spend valuable resources to protect an area that does not need to be protected? For example, the White Ibis has year-round populations along the coast of the southern United States and Mexico, as well as a population in northern South America. They are migratory birds, and spend part of the year more inland in the United States, yet it is only a few months of the year (The Cornell Lab of Ornithology, n.d.). If these birds were to become endangered, it is likely that there would be conflicts in determining how much of the yearly range should be protected and why.

The area of occupancy of the White Ibis (Eudocimus albus) (http://geocat.kew.org/editor)

The area of occupancy of the White Ibis (Eudocimus albus) (http://geocat.kew.org/editor)

The extent of occurrence of the White Ibis (Endocimus albus) (http://geocat.kew.org/editor)

The extent of occurrence of the White Ibis (Endocimus albus) (http://geocat.kew.org/editor)

Another factor determining the geographic range is it’s shape. The shape of the geographic range generally constrained from the North and South, or from the East and West. North-South constraints are frequently controlled by the macroclimate (ex. temperature and precipitation), whereas East-West constraints are controlled by topography and availability of suitable habitat (Brown et al., 1996).

Habitat controlled by macroclimate, creating North-South constraints

Habitat controlled by macroclimate, creating North-South constraints

Habitat controlled by topography, creating East-West constraints

Habitat controlled by topography, creating East-West constraints

A problem in present times stems from climate change, which may alter the range shape due to rising temperatures. If a northern bird’s climate suddenly becomes too warm to endure, they may move north in order to compensate. If they were protected in their original habitat, however, the protected area may not cover their new habitat, which may result in population losses. A study done by Møller et al. in 2002 indicates just that: rapid climate changes are associated with dramatic population loss of migratory birds in the Northern Hemisphere. This can be a difficult situation for policymakers, especially if the population is both moving and declining at rapid rates.

Brown et al. further describes the issues of range size and boundary by commenting on the fact that the range edge is never defined. The internal populations of a geographic range tend to be steadier, with larger, constant populations. However, the outer edges of the range are mercurial, which makes it very difficult to determine. This brings us back to the extent of occurrence vs. area of occupancy issue. While individuals are seen at the borders of ranges, or in an excluded area, it does not necessarily mean that they are within the “geographic range” of their species. Since the edges change constantly, policymakers generally need to decide if they want to protect the bulk of the population, or the entire area that they cover.

At the smallest of scales, genetics also plays a role in conservation. While species can change and evolve into different species over very long periods of time, the genetic analysis tools we have today can show that what we thought was one species is actually two. For example, the California newt (Taricha torosa) was divided into two species in 2007. The newts living on the coast keep their Latin name, while the separate species living in the sierra has been named Taricha sierrae. (Kutcha, 2007). Modern speciation events like this can also have an effect on policy. If both species are endangered, policymakers would need to protect both species instead of just the one beforehand, which leads to more money spent and another proposal to be passed.

It is no wonder, now, that policymakers take so long to get a species protected. The factors discussed above are only a few of the considerations they must take into account in order to pass a proposal supporting protecting part of, or the entire geographic range of a species. With all that being said, every bit of science contributing to conservation is important science, which is why we do it.

Literature cited

Brown, J. H., Stevens, G. C., & Kaufman, D. M. (1996). The geographic range: size, shape, boundaries, and internal structure. Annual review of ecology and systematics, 27(1), 597-623.
Gaston, K. J. (1991). How large is a species’ geographic range?. Oikos, 434-438.
Møller, A. P., Rubolini, D., & Lehikoinen, E. (2008). Populations of migratory bird species that did not show a phenological response to climate change are declining. Proceedings of the National Academy of Sciences, 105(42), 16195-16200.
Shawn R. Kuchta (2007). “Contact zones and species limits: hybridization between lineages of the California Newt, Taricha torosa, in the southern Sierra Nevada”. Herpetologica. The Herpetologists’ League. 63 (3): 332–350. doi:10.1655/0018-0831(2007)63[332:CZASLH]2.0.CO;2.
The Cornell Lab of Ornithology. (n.d.). White Ibis. Retrieved March 25, 2017, from https://www.allaboutbirds.org/guide/White_Ibis/id

Percentage of Seabird Species Ingesting Plastic Expected to Reach 99 Percent by 2050

By Laura Vander Meiden, SRC Intern

A recent study has found that if current rates of plastic introduction into the ocean continue, by 2050 approximately 99 percent of all seabird species will have ingested plastic. The study, published in September of 2015, uses a computer model based upon an analysis of data provided by past plastic-ingestion studies to come to these conclusions.

Unaltered remains of an albatross chick at Midway Atoll. Photo by Chris Jordan of the US Fish and Wildlife Service.

Unaltered remains of an albatross chick at Midway Atoll. Photo by Chris Jordan of the US Fish and Wildlife Service.

Plastic debris harms seabirds and other marine organisms through both entanglement and consumption. Entangled birds can lose motor abilities reducing their ability to feed and fly. Consumption of plastic can lead to pieces accumulating in the digestive system, taking up gut space typically available for food. This negatively impacts an individual’s body condition and severely reduces its ability to care for itself. In some cases, the plastic completely blocks the digestive system, leading to death. Additionally, plastics in the ocean absorb harmful chemicals that can leach out and cause damage to a seabird’s internal organs. Since approximately half of all sea bird species are in decline, these deleterious effects of plastic debris on seabirds are very concerning.

An analysis of data published in studies from 1962 to 2012 shows that 59 percent of the seabird species studied had been found to ingest plastic. Likewise, researchers found that 29 percent of the individual birds sampled in each study contained plastic in their digestive systems. Trends in this data show an average increase of 1.7 percent a year in the proportion of individuals studied that had ingested plastic. To put this in perspective, if that trend continued and those studies were to be redone today, plastic would be found in over 90% of the individual birds sampled.

Using this data, researchers created a computer model to determine areas of risk for seabird species worldwide. The model included 186 species of sea birds. Surprisingly the location of highest estimated impact was not in the Pacific Ocean, home of the infamous Great Pacific Garbage Patch, but at the boundary of the Southern Ocean between New Zealand and Australia. Though concentrations of plastic debris here are lower than other sites, this area is home to a large number of seabird species that are prone to plastic ingestion. This increases the area’s risk above those of locations with higher plastic concentrations.

plastic figure 2

It is important to remember that seabirds are not the only marine organisms affected by plastic debris. An assessment conducted by the United Nations Convention on Biological Diversity found that in 2012, 663 species were affected by marine waste, with 80 percent of the impact coming from plastic marine waste. This is up 40 percent from a previous assessment completed in 1997. Half of all marine mammal species, every species of sea turtle, and one fifth of seabird species were reported to be affected. Fifteen percent of these species are on the International Union for Conservation of Nature (IUCN) Red List, meaning they are at risk of extinction. Species of highest concern include the Hawaiian monk seal, loggerhead sea turtle, and white-chinned petrel.

The seabird study states that ingestion rates rise with increased exposure to plastic. Therefore, if the introduction of plastic into the marine ecosystem was reduced, the study’s projection that by 2050, 99 percent of seabird species will be ingesting plastic could possibly be avoided. Unfortunately, the problem will only continue to get worse unless waste management practices improve and plastic production is reduced. Commercial plastic production first began in the 1950s, over 60 years ago. If current rates of production continue, during the next 11 years we will produce the same amount of plastic as has been created since plastic production first started. Because plastic doesn’t easily biodegrade, this will effectively double the amount of plastic found on Earth.

The United Nations proposed several actions to begin to alleviate this problem. The proposed actions include reduction in the use of plastic as a packaging material, increased producer responsibility, and improved consumer awareness. These solutions are in contrast to past proposals that have only focused on waste management. However in order for a serious impact to occur, change will likely have to take place at international, national and local levels.

Works Cited

Wilcox, C., Van Sebille, E., & Hardesty, B. D. (2015). Threat of plastic pollution to seabirds is global, pervasive, and increasing. Proceedings of the National Academy of Sciences, 112(38), 11899-11904.

Secretariat of the Convention on Biological Diversity and the Scientific and Technical Advisory Panel—GEF (2012). Impacts of Marine Debris on Biodiversity: Current Status and Potential Solutions, Montreal, Technical Series No. 67.

Challenges in seabird by-catch mitigation

By Hanover Matz, RJD Intern

In this paper, the authors comment on the current conservation status of seabirds and attempts to limit seabird deaths due to by-catch. Two species of seabirds, the albatrosses and the petrels, are particularly vulnerable to the detrimental effects of fisheries such as longlining. These birds normally lay only one egg per clutch and breed infrequently. They have long maturation and generation times compared to other birds, making it more difficult for their populations to recover from high mortality. They are also capable of flying long distances in search of food, crossing many different marine environments. This makes it difficult to implement conservation methods that can protect these birds in every part of the world they inhabit. Some of these species are already considered endangered or critically endangered. In order to fully protect them, an international effort is necessary.

A wandering albatross (Diomeda exulans) off Tasmania, Australia. Photo courtesy of JJ Harrison via Wikimedia Common

A wandering albatross (Diomeda exulans) off Tasmania, Australia. Photo courtesy of JJ Harrison via Wikimedia Commons

Seabirds and human fisheries come into conflict in many of the most productive regions of the ocean, specifically around New Zealand and Australia, the Humboldt Current off Chile, Peru, and Ecuador, the North Pacific, and South Africa. Seabirds are known to be killed as accidental by-catch in longline fisheries, and growing evidence has shown incidental catch of seabirds by trawlers. One difficulty in assessing whether trawling or longlining presents a greater threat to seabirds is the low proportion of entangled seabirds actually recovered from trawling gear. If the birds that collide with the gear cannot be retrieved, it is hard to assess the impact the fishery has. Refining the collection of data on how many seabirds are killed by longlining and trawling will improve conservation efforts.

In South Africa, the use of bird-scaring lines (BSLs) in fisheries has been shown to reduce the mortality of seabirds up to 95%. The trawl fishery previously had proportionally high incidental catches of albatrosses, making this a significant success in terms of protecting threatened species. However, to fully determine how well seabird mortality has been reduced, better data needs to be collected on both the level of by-catch and fishing effort. To reduce the by-catch of seabirds and improve conservation worldwide, the authors stress four important strategies. First, mitigation methods need to be improved with better data and techniques, considering each fishery individually and adapting the methods as necessary. Second, the quality of data collected needs to be increased by improving the programs used to collect it. Third, the fishing industry needs to be engaged by implementing and enforcing by-catch reduction, as well as cooperating to suit the needs of both the fishery and conservation. Finally, cooperation between governments, administrators, and decision makers is necessary to promote better fishing practices and conservation measures. In some fisheries, seabird by-catch mitigation is minimal or nonexistent. While trawling and longlining have been addressed, the effects of purse-seine and gill net fisheries are poorly understood. The threat posed by small scale and artisanal fishing fleets has also not been widely considered. If threatened seabird species are to be protected, it will require both national and international efforts. By improving the science behind the conservation, and cooperating with both governments and fisheries, scientists and conservations will be better able to address this conservation issue in the coming future.

References

1. Favero, M., & Seco Pon, J. P. 2014. Challenges in seabird by‐catch mitigation. Animal Conservation, 17(6), 532-533.