Save the Butterflies

Over the last 20 years, the population of Monarch Butterflies (Danaus Plexippus) in North America has declined by approximately 90% (Moore, 2019). This reason for this decline has been identified to be the loss of their wintering grounds in Mexico and the increased used of herbicide, which is toxic weed control, in the Midwest. Monarch butterflies are herbivorous and are very fond of milkweeds, which are a type of toxic flowering plant which is native to North America. To be clear, the toxin has no effect on the butterfly’s but, can be harmful to humans and grazing animals. Monarch butterflies are partial migrants, meaning not all will migrate. Eastern populations migrate over to high elevation forests in Mexico, and western monarchs’ winter in the trees on the coast of California (Malcolm, 2018).

Migratory behavior in these butterflies is driven by one factor, the abundance of milkweed host plants. With North American agriculture growing and adopting GM crops the fields over which the butterflies migrate have become a toxic warzone. The soil around Genetically modified crops are host to a bacterium called Bacillus thuringiensis which is a natural form of pest control. The bacteria consist of a spore and a protein crystal within the spore that is toxic to insects and other organisms deemed “pests”. It was concluded that the risk this bacteria posed to monarchs was negligible because the exposure probability was too low in the event of pollen specific expression but, this assessment was never put into context of the spatial and temporal variations in the life history of these butterflies (Malcolm, 2018).

There has been no research on the bacterium and mortality of butterflies but, given constant exposure due to milkweed being very common in the Midwest region, there could be consequences in the future. Many other pesticides are also toxic to these organisms. Approved barrier treatments for mosquito control with synthetic pyrethroid permethrin that was sprayed on milkweed in Minnesota showed that 95% of monarch larvae were killed between 50% and 0.1% dilutions (Malcolm, 2018). With the temperature shifts due to global warming, it is expected to see milkweed shifts northward in North America. With this shift northward monarchs will now have to migrate across less suitable habitats in their searches.

 

JIM HUDGINS / USFWS MIDWEST REGION

Monarch Butterfly on swamp milkweed

 

In Mexico, forests cover, and the contiguous canopy is necessary to modify the temperature extreme where the monarchs overwinter. The closed canopy is thought to be important to minimize lipid usage during overwintering, so monarchs do not waste these lipids from unnecessary thermoregulation (Malcolm, 2018) The population of butterflies that winter in Mexico is protected within the “Monarch Butterfly Biosphere Reserve” located in Trans – Mexican Volcanic Belt. Despite logging bans in high elevation fir forests in Mexico, between the years 1986 and 2012, 4,300 hectares of protected forests have been altered from human activities such as logging both large and small scale leaving less than 10% of the canopy intact (Malcolm, 2018). In California, Monarchs winter in over 400 locations within the state and are seen to roost on introduced blue gum eucalyptus, Monterey pine, red gum eucalyptus, and Monterey cypress.

Monarch populations in both the east and west have declined and this only seems to be accelerating. The declines in milkweed resources across the Midwest and specifically around fields where herbicides are used are not helping the problem. Human activities in Mexico and California are also directly linked to the decline of these butterflies despite conservation efforts.  Conserving their migration is only possible if migratory conditions are fully understood and If something isn’t done these butterflies will disappear forever and other species will soon follow.

 

References

Malcolm, S. B. (2018). Anthropogenic Impacts on mortality and population viability of the monarch butterfly. annual review of entomology, 277-302.

Moore, A. (2019, april 9). Fall of the monarchs. Retrieved from wildlife.org: https://wildlife.org/fall-of-the-monarchs/

 

Ringed seals and Global Warming

As of March 2019, the global temperature has risen about 1.62 degrees Fahrenheit since the late 19th century (Global Climate Change, 2019). This number might not sound big but, when it comes to climate and all the organisms who inhabit this planet this number is huge. Changes in temperature can have influence over the seasons, specifically the winter season, and how much snow fall occurs. Researches have predicted there would be less snowfall in the arctic and with decreased ice coverage this could lead to a terrible time for the focus of this post, Ring seals.

Polar bears may come to mind first when thinking of animals affected by climate change, but ringed seals are negatively affected, too—directly impacting polar bears.

© Ian Stirling

 

Ringed seals are widely distributed in the Arctic and, call the Northern Hemisphere’s circumpolar oceans home. These seals have a lifespan of around 40 years and can grow up to 5 feet and weight up to 150 pounds. This species of seal relies heavily on sea ice and with global warming melting the ice in the arctic, this species will begin to show negative effects. These seals spend most of their time under the ice and self-maintain their breathing by scratching at re-freezing sea ice with their claws (Sterling, 2017).  In early April, females will give birth to their pups in small caves that are dug underneath snowdrifts. These caves are used to provide protection to their young from predators in the area. Rain is also possible in the area because of fluctuating temperatures and washes away birth lairs leaving the pups exposed to predation from polar bears, and arctic foxes (Sterling, 2017).

In 2005 a study was done using 639+ ringed seals focusing on their recruitment in the western Hudson Bay area. Data from previous years indicated trends of less snowfall for the area for the months April and may which be when pups are born and nursed (Ferguson, Stirling, & McLoughlin, 2005). The data from 1999-2001indicated decreased snow depth in April and may which resulted in shallower snow drifts and consequently less protection for pups (Ferguson, Stirling, & McLoughlin, 2005). With increasing temperatures, premature breakup of the ice also lead to significant impacts on growth, condition, and overall survival of nursing pups in the eastern Beaufort sea area (Ferguson, Stirling, & McLoughlin, 2005).  Ringed seals need approximately 20 to 30 centimeters or snow to create their lairs for their pups and with the increasing temperature that may not happen due to the decrease in snowfall around the area. As this trend of warming continues, the arctic will continue to increase in temperature and the many species of seal and other organisms that live in the area will be greatly impacted and increased conservation efforts will be needed.

Figure 1: Example of a perfect snowdrift for concealing a ringed seal birth lair and protecting the occupant. (© Ian Stirling)

 

 

References

Ferguson, S. H., Stirling, I., & McLoughlin, P. (2005). CLIMATE CHANGE AND RINGED SEAL ( PHOCA HISPIDA ) RECRUITMENT IN WESTERN HUDSON BAY. Marine Mammal Science, 121-135.

Global Climate Change. (2019, april 21). Retrieved from NASA: https://climate.nasa.gov/evidence/

Sterling, I. (2017, January 10). What About the Ringed Seals as the Arctic Climate Warms? Retrieved from Polar Bears international: https://polarbearsinternational.org/news/article-climate-change/what-about-the-ringed-seals-as-the-arctic-climate-warms/