Monarch Butterfly Population Challenges

BY-LINE:

There are two breeding migratory populations of the monarch butterfly in north America. The butterfly’s dynamics and trends of the monarch’s decline were monitored within the overwintering colonies.

Extreme climate conditions in Canada, The United States and Mexico in overwintering sites in Mexico all contribute to the steady decline in abundance of monarch butterflies. 

Tafadzwa Shanji highlights the population declines and conservation strategies and discusses research efforts to predict how decreasing temperatures are declining the monarch butterfly population.

PARAGRAPH   1: CLIMATE CHANGE

What is climate change?

Climate change is a significant long-term change in global or regional expected patterns of average weather in a significant period. A change apparent from the mid to late 20th century onwards and attributed largely to the increased levels of atmospheric carbon dioxide produced using fossil fuels.

Human activities:

Human activities can influence the climate by changing concentrations of CO2 and other greenhouse gases in the atmosphere, these human generated gases enhance the natural greenhouse effect and further warm the surface, the warming that results from increased concentrations of long-lived greenhouse gases can be amplified by other processes altering the concentrations of aerosols and altering the reflectivity of Earth’s surface. This human-induced change offsets some of the warming from greenhouse gases.

Climate change on monarch ecosystem:

Monarchs need to live in a constant temperature, which is why they need to migrate to a warmer place in the winter. However, these places are beginning to fluctuate more in temperatures. As well as their habitats, climate change is also influencing the butterfly’s main source of food. Making it unbearable for the butterflies to survive.

The black line shows global mean temperatures that have been observed to date, followed by projections to 2100: the blue band is a low emissions scenario and the red band is the high emissions scenario. Scientists are currently tracking along the high emissions scenario. which gets us to well over 4 °C by 2100. Source: Intergovernmental Panel on Climate Change

By 2100, sea levels could rise by a metre, displacing 10% of the world’s population. Countries such as the Maldives will be submerged, and the Indian subcontinent will be left fighting for survival. People will also die in greater numbers as they struggle with the increasing heat.

The ecosystem will collapse and a third of all life on earth will face extinction. Plant growth will slow, then stop. Plants don’t absorb carbon dioxide very well so begin to emit it – making global warming worse.

The world’s food centres will become barren and, within 85 years, one third of the planet will be without fresh water.

PARAGRAPH 2: THE ORGANISM

Monarch butterflies are a charismatic and extensively studied species, representing the quintessential migratory insect. They are known for the incredible mass migration that brings millions of then to California and Mexico each winter.

Habitat:

The monarch butterfly is found in North America from Southern Canada and the Caribbean. In the spring and summer, the monarch butterflies’ habitat is open fields and meadows with milkweed. In winter it can be found on the coast of Southern California and at high altitudes in central Mexico. Monarch butterflies need a delicate balance between cold and hot temperatures. The butterflies are cold blooded, they do not use much energy when they are in cool environments therefore, cool temperatures help monarchs survive. However, cold temperatures can also be very dangerous, if temperatures are too cold, they can freeze to death. Warm temperatures are dangerous too. If temperatures are too warm during the winter, the butterflies will burn their stored fat too quickly. Like running out of gas, they won’t have enough to survive the winter and migrate north in the spring. Environment according to temperature

Environmental Adaptation:

Cold blooded monarchs have special behavioural adaptations for warming up. Monarchs can bask in the sun. When monarchs bask, they open their wings and tilt them toward the sun. like solar panels, monarch capture the sun’s energy by exposing the surface are of their wings directly to the sun however, darker colours absorb more of the sun’s energy than lighter colours do, as the solar energy is absorbed, it is then turned into heat energy. The monarch dark coloured wings are an important aspect of their environmental adaption and survival.

In addition to that, the butterflies can also choose to shiver. The monarchs flight threshold is about 13 degrees Celsius which means that this is the lowest temperature at which monarchs can fly. To fly well they need to attain temperatures in the upper 20s or even 30s. Both adaptations help a monarch raise muscle temperatures to fight threshold. Outside the forest, temperatures can fluctuate rapidly between day and night. Inside the forest, temperatures don’t change as much. Dr Lincoln Brower says the monarch’s forest is like an umbrella and a blanket. It protects the monarchs from cold and moisture. 

PARAGRAPH 3: CONSEQUENSES OF ORGANSIM

Climate effects of Monarchs:

Monarchs are highly sensitive to weather and climate. They depend on environmental cues (temperature in particular) to trigger reproduction, migration, and hibernation. (WWF,2019) The butterflies migrate every six months from the Midwest down to central America through corn and soybean belt. Monarch butterflies arrive in Mexico in November and stay until March. They survive all winter in hibernation with little to no food. The butterflies must depend on the food they ate before their arrival in Mexico. However, because of climate change the fat stored in their bodies is burning out quicker than expected. As temperatures in the overwintering sites increase, the butterflies burn out all their stored fat, since the butterflies are more are more likely to leave the warmth of the trees and scavenge for nectar and water (Monkia, 2018) and won’t have enough to survive the winter and migrate in the spring. This may result results in a smaller time gap for the butterflies lay their eggs and continue their (eat throughout journey)

Analyse data:

There is a negative trend in the data with an average decline in precipitation of .25 inches per decade. This decline it may not seem like a lot, however, it has a highly impact of vegetation over time. The precipitation has been below average 6 of the last 8 years and only average the other two years. The monarch population has been steadily declining through this period.

There are many factors towards the contribution of the decline of the monarch butterflies however, Extreme weather conditions are a major threat to this butterfly throughout its range.

One hundred and fifteen hectares of forest in the monarch reserve were affected by floods, strong winds, droughts and fires.

The three lowest overwintering populations on record have been recorded in the last 10 years.

The 2015-2016 population estimates showed an increase of 225 percent in overwintering habitat from the previous year. (FWS, 2019)

This is great news; however, it is estimated that more than a million monarch butterflies were hit with a deadly freeze in Texas and Mexico just as spring migration was beginning in March.

From 2009 to 2011, and 29 ha more were affected by drought in 2012 and 2013.

In 2014, 2.81 ha more were degraded by drought, severe rain, snow and freezing temperatures caused by mass mortalities of monarch in the overwintering sites, including a severe storm that killed an estimated 2.5million butterflies in January 1891.

Eighty three percent of butterflies perished in 1992 due to extreme cold weather, storms and extreme cold temperature in January 2002 and in January 2004 were the cause of the reduced areas occupied by monarchs in 2002-2003 and 2004-2005 seasons.

 Less storms were observed in 1995.

In this graph it shows that the temperature of the western region for summer has increased since 1990 and have been higher than normal for 8 years in a row. If the comparison of figure 2 and this graph, there is a correspondence between the mean summer temperatures and the number of monarchs the following winter/fall. When temperature levels are below normal the population increases in size and when it is above normal it decreases in size. The population increases slightly in 1993, the coolest year in the period and then declined again in the hot year that followed. High temperatures and drought result in a higher metabolism, lower nectar availability, reduced host plant quality, shorter lifespan and an overall reduction of realized egg/lifetime.

50 year’s time:

If the trend in figure 2 continues, all monarch population have a 63 percent chance of extinction in 20 years and more than 80 percent in 50 years. Climate change is threatening to disrupt the monarch’s migration and render its overwintering habitats unsuitable by the end of the century.

INTERVENTION:

On the behalf of the monarch butterflies. Organisations such as Save Our Monarchs and Monarch Butterfly Conservation Fund have made several efforts to conserve monarch populations by distributing free milkweed seeds and investing in projects to increase the availability of high quality monarch habitats.

priorities for climate-informed monarch conservation should include restoring and increasing the extent of habitat with appropriate milkweed species and nectar sources. The public at large can contribute to this effort by planting backyard habitat. Increased monitoring of populations is also important, and citizen science efforts can contribute to this. It is also essential to maintain and restore overwinter habitat, reduce the use of herbicides and pesticides, and address issues related to land-use change. (WWF, 2019)

CONCLUSION:

Several factors contribute to the decline of Monarch Butterfly populations. However, Climate change poses severe risks as the climate rises, there comes a great threat to the butterflies. As climate change continues taking place, the Monarch Butterfly is being heavily threatened. Governments, industries, and citizens can take more immediate steps to mitigate other threats to butterflies. More responsible logging practices, reduced herbicide use, and Milkweed preservation would give the Monarch Butterfly population a chance to recover.

REFERENCES

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