The Use of Fire Management to Restore Monarch Butterfly Populations - Va Vang Environmental Studies Department CSU, Sacramento ENVS 190 - Senior ...
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The Use of Fire Management to Restore Monarch
Butterfly Populations
Va Vang
Environmental Studies Department
CSU, Sacramento
ENVS 190 – Senior Thesis
May 17, 2018
1
Table of Contents
Page #
I. Abstract 3
II. Biology 3-5
III. Distribution & Generational Migratory Populations 5-8
a. Monarch Generations
i. Generational Migration Routes
IV. Milkweeds 8-12
a. Ethnobotany – Humans and Milkweeds
b. Common Asclepias Species
V. Status & Decline of Milkweed & Monarchs 12-15
a. Wildlife Friendly Agricultural Practices
VI. Prescribe Fire Management 15-17
VII. Propagating Milkweeds 17-18
a. From Root Cuttings
b. From Seeds
VIII. Restoration: Fire on Milkweeds in Prairies 19-21
IX. Other Restoration Efforts/Ideas to Consider 21-23
a. Agricultural Landscapes – data required for restoration
X. Conclusion/Discussion 23-24
XI. Figures & Tables 8, 25-32
XII. References 33-40
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Abstract
The interaction between monarch butterflies (Danaus plexippus) and its host plant,
milkweed (Asclepias) species, are extraordinary during their migration route from Central
Mexico, to United States, onto Canada and then back down to Mexico. The purpose of this thesis
is to explore the root behind declining eastern monarch populations in relations to milkweed
species native to those states. Prairie land conversions and herbicides from agricultural fields
have been the two-main cause of milkweed habitat loss. Conservation research has shown the
benefits of using prescribe fire on these ecosystems to restore milkweeds to support and increase
monarch populations.
Biology
Monarch butterflies (Danaus plexippus) captivate many people because of their
phenomenal migration from Mexico, to the United States, and onto Canada. They then migrate
back to Mexico to overwinter at the end of the year. It is astonishing for an insect with such a
small mass to fly up to 6,000 miles from their two-way migration (Oberhauser & Solensky,
2004). They also contribute as essential flower pollinators for plant ecosystems (Hopwood,
2013). As pollinators, monarchs play a significant role. Impacts on their population will signify
similar impacts on plants that they are pollinators for. If the impacts negatively affect the plants
that monarchs pollinate, then many seeds cannot be dispersed or reproduce.
Monarch butterflies undergo four stages of metamorphosis: the egg, larva, pupa, and
adult stages. They are known as the “milkweed (Asclepias species) butterfly” since they have a
symbiotic relationship with this forb. Milkweeds serve as a significant host plant for monarch
larvae during reproduction and breeding events during their migration.
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Females oviposit eggs underneath milkweed leaves that are tender and healthy with only
1 egg per plant (Urquhart, 1960; Pitman et al., 2018). Eggs are about the size of the head of a pin
and have a yellow base when laid. The color changes to grey as the embryo develops. The
growth of the embryo differs with changes in temperature. The development rate occurs more
rapidly during higher temperatures, compared to lower temperatures (Urquhart, 1960)
Larva, or caterpillar, hatch once the egg becomes grey. This stage consists of 5 instar
stages. Instars are the developmental phases of larva leading the final physical caterpillar form
with high pigmentation of the black, white, and yellow color with fully grown antenna
(Urquhart, 1960). Once the larva emerges, they consume their vacant shell and depend on
milkweed leaves as food resources. This plant is their main and only source of nourishment up
until the next phase. This process lasts about 2 weeks before the pupa stage (Borders et al.,
2013).
Larvae tends to remain on the underside of milkweed leaves even during feeding
activities. They consume only tender parts of the leaves and known to finish one leaf in about
four minutes, which lasts them for a maximum of 2 hours. Just like the growth of the embryo
during the first stage, temperature also plays a crucial role in the rate of growth. If their host
plant is expose to high temperatures, larvae will be more active and gradually grow at a rapid
rate. There are very few larvae that are found in shaded areas. Monarch adults chooses wisely
when laying their eggs onto milkweed leaves and aims for the plants that are unsheltered from
sunlight (Urquhart, 1960).
The pupa, or chrysalis, phase is the final formation of larvae into adult butterflies. Their
physical appearance is orange with black vein markings once they are free from the chrysalis.
Finding the perfect area for metamorphosis is significant. Larvae will leave behind its original
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host plant when matured and travel to other milkweed plants (rare) or found on logs, tree limbs,
window-sills, timbers, and fences to morph. They start out by spinning silk fibers to create a mat
which will then cover the larva. The larva will hang upside down by its prolegs. This stage lasts
between 10-14 days until the adult butterfly emerges (Urquhart, 1960). The lifespan of each
monarch lasts between 2-6 weeks after morphing into a butterfly.
Distribution & Generational Migratory Populations
Monarch butterflies is dispersed in Central Mexico, United States, and Canada.
Distribution of the species vary because of multi-generational populations and from breeding to
non-breeding grounds (Webster et al., 2002). This proposed evaluation will focus on the eastern
monarch population that are from Central Mexico migrating to the U.S
The eastern U.S. population include the monarchs from Central Mexico traveling to the
southern, central, and northeast of the U.S (figure 1). They breed east of the Rocky Mountains.
This population is the bigger one of the two, western and eastern U.S. Concern is higher here
since majority of the migratory populations reside in those states.
Monarchs abandon their breeding territories during the end of summer and start migrating
south towards Central Mexico to escape freezing winter because they prefer high temperatures
(Urquhart, 1960). This begins their spectacular journey from Canada, 3,000 miles to Mexico.
Butterfly’s migratory cycle is usually linked to the locations that they settle in during their
journey. Interactions over spatial movement and time are factors that can show the influence of
location (Webster et al., 2002; Flockhart et al., 2013). For instance, monarchs may come into
contact with surrounding species in their selected location. These species can either be predators
or rivals competing for resources. Monarch butterflies feed on nectar from a variety of plants.
Pollinators, like bees, are also interested in nectar resources. Therefore, they both will compete
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for plant species with nectar. However, monarchs rely heavily on monarch patches to breed. The
best areas are the one with high abundance of milkweed and plant species with nectar.
Monarch Generations
There are four monarch generations each year contributing to the stages of this migration.
Not every generation migrate from Mexico to Canada and then back down. Their lifespans are
short and certain generations migrate only to certain states before dying. The population that
travels back to overwintering sites in Central Mexico are the offspring (great-great-great
grandchildren) of the monarchs that regularly overwinter there from the year before. They are the
fourth-generation population from the previous year that will start the first-generation population
for the new year in Southern U.S. They are referred to as parents of the first-generation
monarchs.
During the first part of migration, the parents from Mexico travels to Texas, Florida,
Arkansas, Missouri, Oklahoma, and Virginia where eggs are laid (Flockhart et al., 2013;
Inamine, 2016) and breeding begins for the first generation (figure 2). These areas are part of
their migratory route migrating towards the Midwestern part of U.S. right when they morph into
adults (figure 3). The start of this migration and breeding begins at the end of March until late
April (Inamine, 2016). The adult monarch of this generation dies after their eggs are laid and the
next generation begins from these southern U.S. states.
The second-generation monarchs are known as the grandchildren of the overwintering
population from Mexico (generation 4 from the year before). Their breeding process starts from
April until June and larvae are found in the Midwest and eastern U.S (figure 4). Adults from this
generation emerges in the middle of June to July and begin laying eggs right away on
milkweeds. They can be found in similar areas where they reside during their larvae stage (figure
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5). This generation moves north but does not migrate as far nor overwinter. Energy is used to
maximize and produce their offspring. Their breeding grounds are in the Eastern part of the U.S.
The next group is the third generation. Larvae from this group can be found in certain
southern states but majority in the Midwest and eastern states similar to the 2nd generation (figure
6). Adult emerges during the middle to the end of summer, July to August. Generation 3
monarch eggs are distributed throughout the northern range in the east right after they become
adults, which will become the 4th generation. Some from the 3rdgeneration continues the
migration to Canada. Early monarchs that surfaces are able to produce other offspring for the
next generation. The later monarch adults either start their migration to overwintering sites or
they go into diapause, delayed maturity, because of the cold temperatures then also head south
(figure 7). They remain in this state until the next spring and breed in the overwintering sites
(University of Minnesota, 2018).
The last generation’s larvae stages begin in July until October. Eggs from this generation
are laid from June to August and larvae are found in the same regions as the 3rd generation
(figure 6). Their maturity stage starts to appear from August to April. This generation are the
population that overwinters and migrates south towards the overwintering colonies in Mexico
(figure 7). This occurs during the autumn season and are the only monarch generation who
overwinters. Majority of this population will undergo diapause. Migration to overwinter in
Mexico begins in September until November and they reside there until spring. This generation
will migrate back north in the spring and will lay eggs that begins the new generations for the
new year.
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Generational Migration Routes
Generation Migration Overwinter? Larvae Stage Adult Stage
1 North No March – April April – June
2 None No May – July June – July
3 Some – Some July – August July – August
North/South
4 South Yes July – October August –
April
Table 1: This table represents the migration routes of the eastern monarch population.
Time when larvae and adult butterflies emerge are also shown.
Milkweeds
Milkweeds (Asclepias species) are perennial herbaceous herbs that grows from a deep
rhizome (USDA, 2006). They can be grown throughout the year and can produce beautiful nectar
which attracts pollinators (Gaertnar, 1979) and migrating monarch butterflies. They are known as
stepping stones for monarchs to support and maintain their population. Milkweed species can be
found in a broad range of habitat including prairies, wetlands, riparian areas, agricultural fields,
roadsides, pastures, and forest margins (Borders et al., 2013; Bhowmik, 1994). Most of the
Asclepias species are grassland species. There are 72 native milkweed species in the U.S. 30
species occurs in the eastern population region.
Milkweeds are propagated both sexually and vegetatively from seeds with a height up to
2 meters. Milkweed seed pods split open when ripe, then will disclose the seeds inside. Seeds
have fluffy pappus to be carried in the wind. The seeds come secured with silky, white hairs, and
are distributed by wind pollination (Urquhart, 1960; Bhowmik, 1994).
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The plants are called “milkweed” because of its stems and leaves. The milky sap, also
known as latex. The latex consists of a chemical called cardenolides (Bhowmik & Bandeen,
1976; Borders et al., 2013). This complex chemical makes the plant poisonous and dangerous for
many livestock species such as cattle and poultry (Urquhart, 1960) and vertebrates. However,
milkweed stems and leaves are an obligate host for monarch larvae (Borders et al., 2013). The
butterfly larvae consume the milkweed leaves, which does not affect them but are stored inside
the insect larvae. The chemical stays with the butterflies, therefore, the color provides protection
since it signals to predators that they are poisonous. Both caterpillars and butterflies are brightly
colored, and indicate to predators that they are toxic and should be avoided.
Ethnobotany – Humans and Milkweeds
Milkweeds also serve as a beneficial plant for ethnobotanical uses by Native Americans,
such as the Potawatomi and Meskwaki tribe. Ethnobotanical usage of milkweed are for fiber,
food, and medicine. This desirable herbaceous plant is well known for being a cordage-fiber
plant used by Native Americans. This forb is known for its ‘bast’ fibers. Once these fibers are
extracted, they can be turn into cords and ropes which are utilized to make fishing nets, head
bands, hair nets, belts, bow strings, animal nets, feather capes, and dance skirts (Anderson &
Moratto, 1996; Stevens, 2001). Some of these items are made specifically for ceremonial regalia.
Certain products made by these fibers require an immense amount of harvested stalks to be
created. Burning helps maintain the forb to redevelop to obtain more stalks for their fiber.
Milkweed stems are collected during the autumn to winter seasons when the stalks
senesce (Anderson & Moratto, 1996; Stevens, 2000). This usually occurs after traditional fire
management practices in the beginning of autumn. Fire burns senescent plant material to
stimulate new growth in the spring. After burning events, milkweeds appear to have better
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growth (Anderson, 1991; Anderson & Moratto, 1996). Milkweeds can also capture sunlight and
recycle nutrients into the soil for development. The stalks are split to retrieve the fibers and may
be use alone or mixed with other plant fibers. It is then rolled on the thigh and twisted together to
create chordage.
Housewives tend to use milkweed plants to substitute as other vegetables, like asparagus.
Toxicity from this herbaceous plant should always be removed before consuming it as a
replacement of food plants. The toxics are removed by a boiling process which lasts between 2-5
minutes before eating or cooking it with other ingredients (Stevens, 2000; 2001).
Young shoots, fruits, flowers, stems, and roots are preferred for consumption by the
eastern and mid-western Native Americans (Stevens, 2000). The plant was known as a pot herb
and many people sold it in packages for two cents back in the 1960s (Gaertner, 1979). Milkweed
latex can cause pain and discomfort without sufficient preparation. Some species can lead to
death like Asclepias subverticillata. This toxic species is found in the southern U.S. and can be
mistaken for Indian hemp (Apocynum canibinum) which grows in the same habitat.
Certain species, like butterfly milkweed (Asclepias tuberosa) or the butterfly milkweed,
are frequently used as medicine to treat diseases and injuries. Scrofula is a form of tuberculosis
on the neck with symptoms such as chills, weight loss, fever, and swelling of the lymph nodes.
Milkweeds are use as ointments to lower these symptoms. The forb provides generalized
medicinal uses and serve as diarrhea and blindness medicine, use in as an ointment for sore
throat, heal snakebites, apply the root for rashes, remove tapeworm, and treat colic. The plant can
be made into a drink and women can produce more milk for feeding purposes (Stevens, 2000).
The Omahas, Poncas, Dakotas, and Menominis tribes consumes the root of butterfly
milkweed for bronchial and pulmonary issues. When chewed, the root can be placed on wounds
10to cure it. It can also be applied as a remedy for sores and prevent nauseas feelings (Steinuaer,
2013). Milkweeds were acknowledged as one of the most effective and important medicine
(Stevens, 2000; 2001).
Common Asclepias Species
30 species of milkweeds can be found in the Eastern states. Many of these includes
common, swamp, showy, prairie, butterfly, and whorled milkweed (table 2). These are some of
the well-known species that monarchs breed in the southern, eastern, and Midwest U.S.
throughout their migration routes and endangered ones that are critical for the butterflies
(Borders et al., 2013). This analysis will focus on 2 milkweed species in the eastern U.S. that
resides in agricultural fields and prairies. One of which is a common species that’s used
extensively by monarchs and one that is also utilized but endangered and requires conservation
attention. Species that will be evaluated includes common milkweed and mead’s milkweeds.
Common milkweed (Asclepias syriaca) is one of the native species in eastern U.S. utilize
by monarchs. It’s currently distributed across the Midwestern and northeastern states with
climatic requirements of 18 and 32°C (figure 8; Bhowmik, 1994; Borders et al., 2013). This is
within the range of the eastern migratory monarch route. The inflorescence of this species
appears in the upper leaf axils with 20-130 flowers per inflorescence. Blooming occurs from
May until August. Common milkweed grows in sandy, rocky, or clay soils along lakes,
waterways, prairies, roadsides, ponds, and waste areas (Stevens, 2006). Roadsides are significant
for oviposit and easy access (Laura et al., 2000; Oberhauser & Solensky, 2004).
Common milkweed is most favored by monarchs and utilized in the eastern monarch’s
breeding range with great potential for milkweed population colonization and reproduction
(Bhowmik, 1997; Hartzler & Buhler, 2000; Borders et al., 2013). Approximately 92% of
11monarchs that return to overwinter in Mexico has been found to feed on common milkweed
during their larvae stages (Malcolm et al., 1993).
Mead’s milkweed (Asclepias meadii) is a common species found in the eastern tall grass
prairie ecosystems. This current distribution extends from Kansas, Iowa, Illinois, Missouri, and
Indiana (figure 9; Bowles et al., 1998; USFWS, 2018). This plant appears late May to June. Once
matured, the stem bears about 6 to 15 flowers. They prefer wet to moderately dry tallgrass prairie
environments (USFWS, 2018). Pollination is by done by bee pollinators. Growing from seeds
can be difficult and requires 4 or more years to fully grown from a germinating seed to a
flowering plant. However, they can live up to decades (Betz, 1989). This is one of the downsides
to this species, but still beneficial for monarch larvae when mature.
Status & Decline of Milkweed & Monarchs
Monarch butterfly’s decline involves many factors. Monarchs are at risk due primarily
due to pesticides in agricultural and prairie fields and milkweed destruction for human
utilization. Anthropogenic activities have been a threat for the species and this have affected
their migratory populations from Mexico, North America, and Canada locations.
The current status of monarch butterflies is still underway although it continues to
decline. The U.S. Fish and Wildlife Service (2014) petitioned to list the monarch butterfly as an
‘endangered species.’ A Species Status Assessment and Status Review is currently underway
until summer of 2019 to decide whether the species should be listed as endangered (USFWS,
2016).
Monarchs benefit greatly from the milkweeds, which follows with growth and
development and the need of continuous corridors along their entire migratory routes. Because of
this commensalism relationship, if milkweeds start to diminish, so will monarch populations.
12The eastern monarch population has declined dramatically since the 1990s until today (figure
10).
Over the past decades, monarch butterflies have declined by 80% that points to extinction
of the species. Listing them as ‘endangered’ will offer time, possible protection, and a roadmap
for conservation efforts. An estimate showed that there is an 11-57% probability that the eastern
monarch population will collapse within 20 years (Centers for Biological Diversity, 2016).
Habitat destruction of milkweed patches has been the widespread cause of destruction for
monarch communities (New et al., 1995) specifically land transformation to agricultural fields.
Prairie regions are vulnerable to development and expansion of modern agriculture in monarch
migration regions (Smith, 1981; New et al., 1995; Vogel et al., 2007). Monarchs that occupy this
ecosystem are interrupted heavily along with milkweeds (Swengel et al., 2011). These lands are
converted to yield crops for human consumption, which is an important requirement, but can
destroy numerous species that has mutualistic relationships. Mead’s milkweed is a native in these
conversion habitats. It has been listed under the U.S. Fish and Wildlife Service since 1988 with
similar threats such as: habitat loss and hay mowing (Harrison, 1988; USFWS, 2018).
Iowa and Wisconsin are states that have lost majority of their prairie habitats. The
remaining fragmented prairies are less than 5 ha in each state (Rooney & Leach, 2010; Ries &
Debinski, 200l). Exploitation of species’ environment for human use has ruined many of the
native organisms in this ecosystem and can also affect migrating ones, like monarchs.
Wildlife Friendly Agriculture Practices
Hay mowing takes place in June to July in prairie fields which affects the milkweed
during their flowering period. This procedure has the ability to clear away premature follicles
from mead’s milkweeds and this leaves the plants incomplete preventing sexual reproduction and
13seed dispersal (Betz, 1989; Bowles et al., 1998; USFWS, 2018). Without a complete life cycle,
the plant cannot develop fully and serve its purpose as a host plant for monarch larvae. Larvae
depend on fully grown leaves to receive adequate food consumption. They do not feed on
immature leaves and stems. Mowing can create disturbances for prairies and total plant coverage
will be reduce. This also produces different species composition base on timing of occurrence
(Fynn et al., 2004; Van Dyke et al., 2004).
The common milkweed species is grown in the Midwest agricultural landscapes and its
existence on the same lands as agricultural crops has cause yields to lessen (Bhowmik, 1994).
But the presence milkweeds attract pollinators. Farmers despises insects and larvae that are
found on milkweeds and other plant species which could impact their crops. This concern has
caused farmer’s need to get rid of plants that interact with insects. The creation of the herbicide
glyphosate was to enhanced crop fields for further and continuation of human utilization without
disturbances (Wyrill & Burnside, 1977). Glyphosate has been an effective herbicide for humans
but the opposite for insects and weeds. This herbicide has also caused destructions in certain crop
fields which led to the creation of BT crops.
BT (Bacillus thingenienis) crops are genetically modified organisms (GMOs) that were
established to avoid glyphosate. It is a bacterium that is harmful and toxic to many insects and
pests but provide crops with protection from glyphosate and plant quality improvement. This
process is done by identifying and extracting genetic material from a donor organism. Only
genes that resists the herbicide are preferred and then modified into crops (Bessin, 2003).
Although BT crops resists this herbicide, it does kill off many unwanted plants and insects that
humans assumed could impact their crops. Many plant species are invasive and have huge
abundance in certain fields. However, this does not apply that all of them impact the crops
14negatively. But many, including milkweeds, have no choice but to die off in that community
because of these situations.
It was discovered that common milkweed declines in Iowa, one of the Midwest states,
correlated to use of genetically modified BT corn and soybean crop fields. Genetically modified
(GM) crops and glyphosate are the main contributors to the reduction of this milkweed species.
Monarchs rely heavily on common milkweeds found in these two GM croplands. A study
revealed that these croplands consist of 78 times more monarchs compared to other habitats.
There was approximately a 58% decline of the weed in the Midwest and an 81% decline in the
monarch population (Hartzler, 2010). The decrease of both the milkweed and monarch
populations will affect the reproduction rates in Iowa and surrounding states within the same
ecosystems (Oberhauser et al., 2001; Hartzler, 2010), usually the 3rd generation.
After the creation of transgenic BT crops, pollen from these hybrids that expresses the
toxin has impacted the common milkweed species. Glyphosate is the main herbicide that’s used
in agricultural crops (Laura et al., 2000).
Prescribe Fire Management
Prescribed fire on vegetation and landscapes have influenced many of our ecosystems. Its
purpose is to maintain the biodiversity of certain landscapes and significant for natural resource
management (Huntzinger, 2003; Driscoll et al., 2010). Native plants and animals on prescribed
fire landscapes are adapted to fire events. Understanding these species response to fire is
necessary for conservation efforts (Driscoll et al., 2010). This will reveal how fire may impact
species and if it continues. Considering the effects of time, scale, frequency, and conditions of
specific landscapes are important for prescribed burns (Van Dyke et al., 2004). They may
influence the abundance of native species in certain areas (Fynn et al., 2004).
15Fire have been a tool used to manage ecosystems for utilitarian or religious purposes.
Traditional fire management practices were passed down by many generations in indigenous
tribes. These groups of people have traditional ecological knowledge (TEK) of fire usage to
establish specific desired habits for usage. The main uses of fire are to encourage seed
production or to clear agricultural fields. Burning can promote environmental stability,
maintenance of ecotones, and increase diversity and resources (Raish et al., 2005).
The Patch Mosaic Burning (PMB) concept is the influence of space and time of fire
regimes. (Driscoll et al., 2010). PMB fire creates a mosaic of patches which can increase
heterogeneity, this belief is also known as pyrodiversity (Parr & Brockett, 1999; Baum &
Sharber, 2012). The burning of the patches is known to have a variety of habitats that fit the
needs of certain landscapes (Parr & Anderson, 2006). Burn events will supply species on certain
landscapes with their preferred resources.
PMB arises from indigenous traditional burning techniques. These burning concepts are
used universally by many indigenous people (Parr & Anderson, 2006). Mosaic burning has been
used by one of the largest group of indigenous people, the Australian Aborigines. This
management system has been used as technique to clear land for agriculture and hunting. As
civilization developed and evolved over the years, fire management has been viewed as a
destructive method to use (Old, 1969). But now it is being implemented back into management
procedures and shown positive results for habitat and species conservation.
PMB can be a complex concept that consists of two variables: visible and invisible
mosaic (Parr & Andersen, 2006). Invisible mosaic is the term which describes the results of fire
regimes over fuel age by years viewing the frequency, intensity, and lengths of past intervals
(Bradstock et al., 2005; Foster et al., 2017). Visible mosaic refers to the time-since-fire, or post
16fire, status of burned areas. It is easier to determine and see the visible mosaic patches since the
burn in these patches are frequently burned. Invisible mosaics are often covered up since the
burn may be from years ago (figure 11). All characteristics of these two variables explains the
diversity of fire regimes (Parr & Andersen, 2006).
Mosaic prescribe burning was used as a management system with the belief that it
reduces the heavy fuels that are used on certain lands to reduce intense wildfires. It also
generates the growth of vegetation leading to the increase of diversity of plants and animals
(Burrows et al., 2004). It is crucial to understand the how species react to postburn areas and see
the different spatial patterns from the burning (Driscoll et al., 2010). This determine locations
where prescribe fire can be used at to improve biodiversity.
Fire regimes vary across different locations. The size of prescribe fire and its impacts can
either be devastating or beneficial. Large, uncontrollable prescribe fires can destroy species
diversity and infrastructures if they are within parameters of the fire. Small prescribe fires may
not be able to help germinate native species in certain locations. Finding a decent size prescribe
fire will helpful for landscapes to gradually develop. Fire can alter landscapes but also heals the
land. This does depend on education, knowledge, and management experiences.
Propagating Milkweeds
From Root Cuttings
The Asclepias species conservation and propagation by cuttings of the tuberous rhizome
are considered for conservation. This method can be easy and reliable to increase milkweed
populations. Cuttings should be done when the plants are inactive and should be kept cool and
moist. The cuttings are then placed into containers of sand or mix with peat moss. Regular
misting and covering the container is necessary for humidity. The roots will develop shoots
17within 6 weeks. They can then be planted back onto landscapes to increase milkweed
populations (Luna & Dumroese, 2013). The rhizomes should be planted in conservation regions
or gardens by autumn so they will be able to develop enough to survive the colder seasons
(Stevens, 2006). Milkweeds are able to reproduce visible shoot buds and flowers frequently
when their roots are cut then replanted. But this procedure shouldn’t be done often because the
plants will have poor crown development and overwinter imperfectly (Luna & Dumroese, 2013).
From Seeds
Propagating milkweeds from seeds are easy to complete and follow. The following steps
will help anyone grow their own milkweeds for any purpose (Stevens, 2006).
1. Collect milkweed seeds after their pods have matured before opening. Avoid losing
the seeds.
2. Remove grasses or weeds in your chosen area to plant the seeds and cultivate the soil.
3. Seeds can be placed into the soil during autumn and sow the seed with fine sand at a
rate of 1/8 oz per sq. yd.
4. In greenhouses, milkweeds should be cold-treated (low temperatures) for at least 3
months.
5. Milkweed seeds are very capable of surviving. Weed invasive species and water the
seeds as needed.
These two methods of propagating milkweeds usually do not mature and blossom until
the second year. Some may occur earlier depending on the environment that it is placed in. seeds
and cuttings are available in nurseries. They can thrive in semi-dry places and spread from there
increasing the population (Kinscher, 1992; Stevens, 2006).
18Restoration: Fire on Milkweeds in Prairies
Monarch and milkweed management has shown that the decline of one species influences
one another. Many conservation and restoration efforts have been established to enhance the
milkweed species to conserve monarchs that reside in the Midwest, northeastern, and southern
U.S. regions during their migration. Different states in these regions have developed milkweed
conservation solutions to support the butterflies. Many of which includes prescribe fire/burning,
grazing, timber harvest, and roadside milkweed control (USDA, 2015).
Fire management has been a known system used by many farmers in prairie fields since
the 1950s (Bowles et al., 1998). This procedure is the main source of management used in
prairies for maintenance and conservation on milkweeds and other forbs (Kline, 1997; Bowles et
al., 1998). Fire managed prairies in the Midwest has been incorporating it into their procedures to
increase abundance and biodiversity.
Periodic burning can increase monarch habitats when applied to milkweeds. Dormant,
small scale fires reveal that it encourages the development of flowering (Betz, 1989). The
burning will be able to germinate the seeds on landscapes by the heat or smoke it generates. This
increases seeds and biomass productivity (Old, 1969; Rooney & Leach, 2010). Low intensity is
preferred and creates faster yet cooler burning for milkweeds.
Plant responses to prescribe fire varies since it is influenced by the season in which it is
used. Autumn and spring is more common for prescribe burns but forb diversity tends to be
reduced during these seasons. Autumn is the perfect season to use prescribe fire but summer
burns has also shown that milkweed can reemerge for another growth cycle of the same year
(figure 12; Borders et al., 2013; USFWS, 2018). The development during the summer procedure
is best toward late flowering grasses and forbs as they reach the period of senescence (Howe,
191994a; 1994b; Baum & Sharber, 2012). Milkweed is one of the forbs that regenerates growth
during summer burns. In the Midwest, rainfall is not limited which allows the soil content to
have higher organic matter. Infiltration after post burns are less critical and has better growth
compared to areas where rain is limiting (Old, 1969).
In a study, Baum & Sharber (2012) used prescribed fire on tall grass prairie fields in
Oklahoma. This burning was implemented during the spring and summer to create a mosaic of
patches of milkweeds in 200x400 meter plots (total of 6). Data were recorded after patches were
burned, typically in July for both spring and summer, for 3 years. From their results, burned
areas showed higher density of milkweeds while significantly lower in unburned plots. The fire
eliminated the plants and tender leaves resulting in new growth of milkweeds in burned plots.
Availability of the new reproduced plants for monarch use are from August to October. Eggs and
larvae were abundant in the newly produced milkweeds from monitoring. The climax of both
eggs and larvae in the burned plots were at the end of August and early September. Without the
use of fire management, the milkweeds eventually senescence by August.
Monarchs who utilizes these milkweeds in Oklahoma are the 3rd and 4th generations that
migrates south to overwinter in Mexico. They are usually pre-migrants that travels back early to
breed. Summer prescribed fire had the capability of supplying milkweed corridors for the pre-
migrants during a difficult time when the plant is generally unavailable. With new emergence of
milkweeds, the butterflies will be able to reproduce more and increase their populations. The
study concluded that space and time of fire during the summer are vital to help conserve and
generate more milkweed patches therefore leading to the increase of monarch populations (Baum
& Sharber, 2012).
20Fire management has been a successful addition for a variety of monarch habitats. In the
Midwest states, prescribe fire has been beneficial to regenerate milkweeds for late-season
breeding monarchs that are migrating to overwinter in Mexico. This occurs during the summer
season and in tallgrass prairie habitats (USDA, 2015). With the loss of this ecosystem, it can be
detrimental for these last migrators since this is when hay mowing also occurs. Another solution
is to use prescribe fire after mowing of the prairies. This method will help the butterflies breed
when they migrate through prairie landscapes to overwinter.
Other Restoration Efforts/Ideas to Consider
Agricultural Landscapes – data required for restoration & suggestions
Collecting data on the current abundance and population number of monarch and
milkweeds can provide suggestions to take accurate actions. To compensate for the loss of
monarch butterflies in agricultural fields, lost and current remaining population statistics are
crucial data. In agricultural fields, procedures implemented into caring for soybean and corn
fields can affect milkweed species and monarch butterflies. Common milkweed is the species
that’s found on this landscape.
John Pleasants conducted a study to calculate the magnitude of milkweed loss for
possible restoration efforts. He did this by focusing on agricultural landscapes and grasslands in
the Midwest (Pleasants et al., 2017). An estimation of the first usage of the herbicide, glyphosate,
was used to compare the population density of milkweed species from 1999-2014. Iowa was the
only area that was sampled for milkweed data but was used to estimate for other states. Data
were found to be intertwined with the 3rd and 4th generation monarchs who overwinters
(Pleasants & Oberhauser, 2013). Data has shown an 80% decline of milkweed populations from
1994-2014, monarch population decline follows (figure 13; Monarch Watch, 2015). Monarchs
21tend to populate the milkweeds that are located near agricultural crops in the Midwest. Their
conservation goal is estimated to be 6-ha overwintering habitats.
Results showed that abundance of milkweed left in their sampled sites of corn and
soybean fields decreased 96% from 1999-2014 and 99% from 2010-2014 in their sampled
location, Iowa. This is a total of 862 million milkweed stems that has been destroyed during
those years. The total remaining estimation of milkweeds in all the Midwest states is about 1.34
billion. Majority of the areas with higher population size is on conservation lands and roadsides
which provides milkweed and monarchs safe environments to reside in.
The number of milkweeds that needs to be restored is a 32% increase, approximately
4.15-ha, to be able to support the overwintering generations. This would equal to 425 million
stems added. To reach the goal of 6-ha, it would be 1.6 billion milkweed stems (Pleasants et al.,
2017).
Pleasants and his team does not expect for further milkweed loss in agricultural fields
because they have all been extirpated. They suggested that restoration efforts should be the main
focus for what’s been destroyed. To compensate for all the loss of milkweeds in this ecosystem,
it would require efforts and manpower. Because roadsides and Conservation Reserve Programs
(CRP) are spread throughout monarch ranges in the Midwest, it would be more effective to start
restoring milkweed stems to those areas (Pleasants et al., 2017). It will also benefit agricultural
fields within CRP lands. Some CRP lands and roadsides still have milkweeds, while some do
not. Starting out small with a restoration project will help plan for better, more effective projects
after mitigation and observations that may show improvements. With this to consider, the
geographic area for milkweeds are significant for conservation. Having visuals of milkweed’s
22current distribution and loss can provide information for conservationists and scientists to fill in
the gaps that were destroyed.
Conclusion/Discussion
Monarch populations are breathtakingly, beautiful sights to see. Their extreme flight from
three countries leaves everyone in awe. The different generations interaction and linkage to their
host plant, milkweeds, throughout the year showcases the astounding ecological relationship
between two species. Unfortunately, the synergistic relationship between milkweeds and
monarchs leaves them vulnerable. If one disappears, so does the other.
Milkweed species have been declining due to many human impacts involving herbicides,
prairie degradation, or even land exploitation for human utilization. Because the butterflies
require milkweeds to develop, the reduction in population size of one species leads to the same
results as other. This requires conservation and mitigation efforts to help manage both species.
Restoring millions of milkweeds to the eastern part of the U.S. will require attention and
participation by local communities. Some milkweed species, such as Mead’s milkweed, are also
threatened and listed as endangered. Restoration are required for them because they will continue
to influence the monarch populations’ downfall. The sectors that requires attention in the eastern
part of the U.S. are prairies and agricultural fields. The concern has been over two decades
(Thogmartin et al., 2017). The use of prescribe fire for conservation of the forb will be able to
provide a manageable monarch population. Studies have reported the importance of fire usage
and has shown benefits for common milkweed and mead’s milkweed. It can also provide habitats
for other species, such as pollinators. Ecosystem services from these areas can benefit other
organisms, therefore, are significant for our ecosystems.
23Government agencies are efficient with this situation of monarch decline. The USFWS
had restrict the use of pesticides in GM crops (Kurth, 2014; Thogmartin et al., 2017). Less
exposure to herbicides will be one less issue to worry about. Destructions in prairie and
agricultural fields have been reduced and milkweed species has increase along with monarch
larvae.
Although this can be an extremely immense task, it may be achievable if broken down
into segments. Focusing on critically threatened areas will create simpler tasks and opportunities
for this restoration journey. Restoration efforts should engage farmers and roadside managers to
restoration projects while educating them about milkweeds and monarchs. Education is always
key for everything. Informing them about the value of monarchs could decrease or even ban or
reduce the use of herbicide for agricultural lands. This could also influence prairies because they
will understand the activity of hay mowing and know when to and when not to mow (Pleasants
et al., 2017).
24Figures & Tables
Figure 1: North America’s Monarch Populations, western (west of the Rocky Mountains) and
eastern population (east of the Rocky Mountains, Monarch Watch, 2010).
Figure 2: Monarch
Generation 1 – larvae
distribution in southern
U.S. (University of
Minnesota, 2018).
25Figure 3: Monarch
Generation 1 – adult
migration northward and
distribution (University
of Minnesota, 2018).
Figure 4: Monarch
Generation 2 – larvae
distribution in the
Midwest and eastern
U.S. (University of
Minnesota, 2018).
26Figure 5: Generation 2 –
Adult migration
northward and
distribution (University of
Minnesota, 2018).
Figure 6: Generation 3
and 4 – larvae
distribution in the
Midwest, southern, and
eastern U.S. (University
of Minnesota, 2018).
27Figure 7: Generation
3 and 4 – Adult
migration towards
north and south and
distribution
(University of
Minnesota, 2018).
Figure 8:
Distribution of
‘common
milkweed’
species in
eastern U.S.
(Bhowmik,
1994).
28Table 2: This table depicts the 9 available milkweed species and 1 endangered species identified
in the southern, eastern, and Midwest region of the U.S. for monarch butterflies. (Borders et al.,
2013).
Species – Scientific Name Common Name Habitat/Distribution
Asclepias asperula capricornu Antelope horns Upland prairie pastures,
grasslands, and road sides.
Abundant in: TX, OK, KS, NE
Asclepias hirtella Tall green milkweed Upland tallgrass prairie, lowland
prairie, prairie hay meadows,
glades, roadsides, and marshy
areas. Abundant in: MO
Asclepias incarnata incarnata Swamp milkweed Wet meadows/prairies, sloughs
& roadside ditches, swamp
borders, marshes, ponds, and
lakes. Abundant in: TX, some
eastern states
Asclepias speciosa Showy milkweed Short grass prairies, roadsides,
rivers, streams, slough, pond,
and lakes. Abundant in: OK,
KS, NE
Asclepias sullivanti Prairie milkweed Lowland/upland prairies, wet
meadows, creek banks, and river
bottoms. Abundant in: KS,
MO, IL, IA
Asclepias syriaca Common milkweed Prairies, old fields, margins of
woods, flood plains-lakes/ponds,
creek banks, roadsides, and
railways. Abundant in: KS,
NE, IA, MO, IL, WI, IN, KY
Asclepias tuberosa interior Butterfly milkweed Open woods, prairies, savannas,
old fields, and roadsides.
Abundant in: KS, OK, AR, TX,
IL, MS, IN, WI, KY, TN
Asclepias verticillata Whorled milkweed Prairies, glades, open woods,
fields, flood plains, and
hillsides. Abundant in: KS, NE,
IA, MO, IL, WI, IN, KY, OK,
AR, LA
Asclepias viridis Green antelopehorn Prairies, glades, grasslands,
roadsides, and pastures.
Abundant in: KS, OK, AR, LA,
MS, MO
Asclepias meadii Mead’s milkweed – Tallgrass prairie.
endangered Abundant/endangered in: IA,
IL, MO, KS
29Figure 9: Current
distribution of
mead’s milkweed in
eastern U.S.
(USFWS, 2018).
Figure 10: Eastern monarch population that has dwindle since 1994 until 2018 (Center for
Biological Diversity, 2018).
30Figure 11: Image A
showcases visible
mosaic while image
B shows the
invisible mosaic
(Parr & Andersen,
2006).
31Figure 12: (a)
represents burned
plots in spring
whereas (b) represents
plots burned during
the summer (Baum &
Sharber, 2012).
Figure 13: Monarch population decline, 1999-2013 (Borders et al., 2013; Monarch Watch,
2015).
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