The Monarch Butterfly Biosphere Reserve (Spanish: Reserva de Biosfera de la Mariposa Monarca) is a World Heritage Site that contains most of the wintering places for the eastern population of the monarch butterfly. The reserve is located in the Trans-Mexican Volcanic Belt pine-oak forests ecoregion, on the border of Michoacán and the State of Mexico, 100 km (62 miles) northwest of Mexico City. Millions of butterflies arrive in the reserve each year. Butterflies live in only a small part of the reserve’s 56,000 hectares during October through March. The biosphere’s mission is to protect the butterfly species and its habitat.

Most of the monarch butterflies that winter in this area come from eastern North America. Scientists discovered these locations in 1975. In the 1980s and 2000, presidential orders made these privately owned areas a protected reserve. The reserve was named a Biosphere Reserve in 1980 and a World Heritage Site in 2008. The reserve remains mostly rural. Reserve managers are concerned about the harmful effects of illegal logging and tourism. Conservation efforts sometimes conflict with the needs of local farmers, community landowners, private landowners, and indigenous people.

History

The area that now includes the reserve was heavily logged during the 19th century, when it was a colony. After the Mexican Revolution, efforts were made to correct these actions by giving land grants to Indigenous groups, such as the Otomi and Mazahua. These communities have traditionally protected the upper mountain areas as shared lands for use by all, including sustainable forest use, while the lower hills were divided into family plots for growing food crops.

Protection for the monarch butterfly’s wintering areas was first declared in 1980 by President José López Portillo, following years of research on the butterfly’s migration. In the late 1980s, the reserve was managed by the Secretariat of Urban Development and Ecology.

In 1986, poet Homero Aridjis, who founded the Group of 100, persuaded President Miguel de la Madrid to protect the wintering sites. A presidential decree on October 9, 1986, named several areas, including Sierra Chincua and Cerro Altamirano, as protected zones for the monarch butterfly’s migration, hibernation, and reproduction. These areas are part of the Monarch Butterfly Special Biosphere Reserve, covering 16,110 hectares (62 square miles). Core zones of 4,491 hectares (17 square miles) had a complete ban on logging and use of plants and wildlife. Buffer zones of 11,620 hectares (45 square miles) allowed limited economic activities, as long as they followed environmental rules.

In September 2000, the reserve was expanded to cover 56,259 hectares (217 square miles), with core zones of 13,552 hectares (52 square miles) and buffer zones of 42,707 hectares (165 square miles). In 2008, Homero Aridjis, then Mexico’s ambassador to UNESCO, helped the World Heritage Committee designate the reserve as a World Heritage Site, classified as a natural area.

In February 2014, the Group of 100 and Make Way For Monarchs sent a letter to leaders of Mexico, the United States, and Canada, asking them to address the monarch butterfly’s decline at a summit in Toluca. The letter noted that monarch numbers had dropped from 1.1 billion in 1996 to 33 million by 2013–2014. Experts now say the main cause is the growth of genetically modified soybean and corn crops in the U.S. Corn Belt, which led to the destruction of milkweed, the only plant monarch caterpillars eat. Logging in Mexico and illegal logging in the reserve also contributed to the decline.

At the summit, leaders agreed to work together to protect biodiversity and address environmental issues. In 2014, President Obama created a Pollinator Health Task Force, aiming to increase the eastern monarch population to 225 million butterflies by 2020.

In 2016, over 200 scientists and artists signed a letter urging leaders of Mexico, the U.S., and Canada to protect monarch breeding grounds and stop logging in the reserve.

In 2020, there were nine monarch colonies in the reserve, covering 2.10 hectares (5.19 acres). Scientists estimate that 50 million butterflies can live in one hectare, so the 2020 population was about 105 million. By 2024–2025, the colonies occupied 1.79 hectares (4.42 acres), nearly double the 0.90 hectares (2.22 acres) from the previous year.

In 2020, Homero Gómez González, an important conservationist, disappeared. Some believed loggers were responsible, but others say the disappearance was linked to rising violence and organized crime.

As of 2023, the Joya Redonda Monarch Butterfly Sanctuary, located 50 miles (80 km) southeast of Mexico City, is a major overwintering site. Monarchs roost in oyamel fir trees there each winter. After deforestation in the reserve destroyed older hibernation areas, more butterflies began settling in Joya Redonda in the 2000s. With help from volunteers, the number of colonies there grew tenfold in one year. In the 2021–2022 season, only four trees had colonies, but by the next season, there were 42. At that time, visitors paid 100 pesos (about $5.50) to enter the sanctuary.

Ecosystem

The reserve is located in the mountainous forests of eastern Michoacán and extends to western Mexico State, which is 100 kilometers northwest of Mexico City. In Michoacán, the reserve includes the highest elevations in the state, with peaks reaching 2,700 meters above sea level. The climate is temperate and somewhat moist, with a rainy season during the summer. The average maximum temperature is 22°C (71°F). Different types of climates exist in this area: cool and semi-moist, semi-cold and semi-moist, and cold and semi-moist.

The reserve is shaped by basalt rock that forms cracks, breaks, and steep cliffs in a northeast–southwest direction. Older rock formations, such as volcanic cones and lava beds, have been replaced by these basalt structures. The soil is highly permeable, meaning it allows water to pass through easily, resulting in little surface water. Small ponds and arroyos (dry stream beds) are found in some areas. Forests of pine and drought-resistant oyamel fir trees create microclimates that offer shelter during freezing temperatures or winter rains. Scientists are worried that the oyamel fir habitat in the reserve may shrink or disappear by the end of the 21st century, mainly due to climate change.

This area is mostly covered in forests. The types of trees in the forest change with altitude:
– Holm oak up to 2,900 meters above sea level
– Holm oak and pine between 1,500 and 3,000 meters above sea level
– Oyamel fir between 2,400 and 3,600 meters above sea level

Below 2,400 meters above sea level, there are small areas with junipers, cedars, and meadows. Some areas have been changed by agriculture and human settlements.

The wildlife in the area ranges from sub-tropical to sub-arctic species, including several that are found only in this region. These include white-tailed deer (Odocoileus virginianus), coyotes (Canis latrans), long-tailed weasels (Neogale frenata), grey foxes (Urocyon cinereoargenteus), rabbits (Sylvilagus spp.), ravens (Corvus corax), turkeys (Cathartes aura), great horned owls (Bubo virginianus), various types of hummingbirds, reptiles, and amphibians.

There are fourteen major butterfly colonies in these rugged mountain forests, which make up more than half of the colonies in the eastern U.S. and Canada monarch butterfly population. It is estimated that up to a billion monarch butterflies spend the winter here each year. These colonies are very dense, with between six and sixty million butterflies per hectare. The reserve areas are located in the municipalities of Ocampo, Angangueo, Zitácuaro, and Contepec in Michoacán, and Donato Guerra, Villa de Allende, and Temascalcingo in the State of Mexico. These colonies are divided into five main zones or groups.

Eight of the fourteen colonies are within the protected area. The colonies themselves cover only 4.7 hectares, but the protected biosphere area covers 56,259 hectares. Five colonies are open to visitors: Sierra Chincua and El Rosario in Michoacán, and La Mesa, Piedra Herrada, and El Capulin in the State of Mexico. Other colonies near San José Villa de Allende and Ixtapan del Oro are not promoted for tourism due to the risk of harming the butterfly populations. El Rosario is the largest sanctuary in Michoacán, where butterflies cover about 1,500 trees.

Although the Biosphere Reserve still faces challenges with infrastructure, such as trash near parking and merchant areas, recent improvements have been made, especially in the El Rosario sanctuary. These include clearly marked footpaths with security patrols, stone or concrete steps in steep areas to reduce erosion, and the removal of horsepaths to prevent erosion. Only two areas have significant facilities: Sierra Chincua has a research center focused on monarch butterflies and a nursery for reforestation efforts. Cerro El Companario has facilities for tourism.

Conservation

Millions of monarch butterflies travel south from Texas into Mexico, following the Sierra Madre Oriental mountains to a special preserve. The butterflies gather in large groups on pine and oyamel trees. To many people, the trees look orange, and their branches bend under the weight of the butterflies. In spring, these butterflies travel north across America, sometimes reaching Eastern Canada. During their journey, four generations of monarch butterflies are born and die. Scientists believe monarch butterflies use signals like the angle of sunlight, the aging of milkweed plants that caterpillars eat, shorter days, and colder temperatures to begin their southern migration in the fall. (Monarch Butterfly Migration, 2025) Climate change has changed the migration patterns of monarch butterflies. During migration, monarchs fly north when they are exposed to cooler temperatures. Large groups of butterflies may help them stay warm. When the sun warms them, the butterflies fly. The sound of their wings beating has been compared to the sound of light rain.

Conservation efforts, which were first created to protect the butterflies, now focus on saving their habitat. The survival of monarch butterflies depends on many different habitats across North America. Scientists do not know enough about the butterflies. For example, the full size of their wintering areas and the environment there is not well understood. This makes it hard to know how large the preserve needs to be to protect the butterflies.

Since conservation efforts began, progress has been made. While some improvements are still needed, efforts have been made to control trash and limit access to protected areas. One project by the World Wildlife Fund has brought together scientists from different countries to improve the design of the preserve. A monitoring system has been set up to keep the forests healthy and stop illegal logging and forest fires. On the Mexico State side, the largest sanctuary is between San José Villa de Allende and Ixtapan del Oro. It is not promoted for tourism to reduce harm to the area. (StateMex) In winter 2008–2009, scientists plan to tag as many wintering butterflies as possible with lightweight stickers that do not slow their flight. This will help track their exact path as they return north to the U.S. and Canada in spring. Recent counts from the U.S. and Canada show that the number of butterfly colonies has been stable in the 2000s, with about a dozen confirmed colonies in the winter of 2007–2008. The number of colonies changes each year, ranging from seven in 2004–2005 to eight to twelve in other years.

Most of the preserve is home to rural farming communities of the Otomi and Mazahua peoples, especially on the Mexico State side. Many protected areas are not owned by the government, and the reserve is split by a state line, making conservation work difficult. In the Biosphere Reserve in Mexico, the biggest threats to the butterflies are deforestation, illegal logging, unorganized tourism, forest fires, and poor cooperation between groups. Many of these problems come from nearby human settlements that use natural resources.

The needs of local people, including farmers, landowners, and communities, have been considered in conservation efforts, but some conflicts remain. Even though the Mexican government declared the area a biosphere reserve, most of it is owned by 38 ejidos (communal land groups), seven indigenous communities, and 16 private landowners. The main communities in the area are Contepec, Temascalcingo, Angangueo, Ocampo, San Felipe del Progreso, Zitácuaro, Villa de Allende, and Donato Guerra. The closest city is Zitácuaro, which has grown and influenced nearby rural areas.

Many communities in this region are poor, with limited access to basic services, high rates of illiteracy, and childhood malnutrition. In the past, mining provided jobs, but the mines are now empty. These communities have a tradition of cutting trees for wood used in furniture and crafts. High unemployment, especially among young people, leads to migration to other parts of Mexico, the U.S., and Canada. Today, the reserve supports activities like farming, raising livestock, and selling handmade crafts and food to tourists. Communities that agree to help with conservation may receive money through a program called Payment for Ecosystem Services (PES). This program tries to support conservation by paying communities for protecting their forests.

In the early 2000s, the reserve’s border areas were changed to allow seasonal tourism. Five of the eight butterfly colonies are in Michoacán, but only two are open to the public: Sierra Chincua in Angangueo and El Rosario in Ocampo. These areas welcome visitors from November to March, when local guides lead tours. In the State of Mexico, La Mesa and El Capulin are also open to the public. Thousands of Mexican and international tourists, mainly from the U.S., Canada, Spain, France, Germany, and Japan, visit the reserves. The most famous and visited colony is El Rosario. Some scientists worry that tourism harms the environment because it is hard to manage large numbers of visitors without causing damage.

In February, Angangueo holds the Festival de la Mariposa Monarca (Monarch Butterfly Festival). This event started in 1992 to raise awareness about the butterflies, use ecotourism, and celebrate the culture and arts of the area. The festival includes food, music, dance, and art exhibitions. Nearby communities like Aporo, Contepec, Hidalgo, Irimbo, Jungapeo, Maravatío, Ocampo, Senguio, Tuxpan, Tlalpujahua, and Zitácuaro take part. In 2010, the festival featured the Symphonic Orchestra of Michoacan, the Enrico Caruso Ensemble, and an art exhibition called "Papaloapan" by artist Luis Moro. Events also included dance and photography workshops in Angangueo and nearby areas. A new art exhibition has been created to show the connection between the butterflies’ migration and the people of Michoacán.

In January 2016, Google created a special doodle to celebrate the 41st anniversary of the discovery of the Mountain of the Butterflies.

Criticism

Conservation efforts in the Oyamel Mountain Nature Reserve mainly focus on limiting land use, but the communities living there are not involved in managing the reserve. Some public and private groups have tried to encourage forest protection and promote butterfly tourism, but these efforts have had mixed results. Some communities are resisting these restrictions and want to use more land for farming.

Local communities and ejidos have a long history of protecting forests through shared management and responsibilities to care for natural resources. They have formed community defense groups to protect their lands from illegal logging and criminal organizations. The creation of the reserve system has taken land away from indigenous and mestizo communities. These communities have traditions that show humans and nature are equal and live together, not as separate groups. Trees in the reserve need human help to survive threats like insect infestations. Incentive programs to protect the forest have failed because local communities were not given enough power or support.

Through economic reforms, the Mexican government has handed control of the area to NGOs instead of local communities, but this has also increased the responsibilities placed on these communities. Conservation groups have sometimes stopped paying communities even when illegal logging, not the communities’ own logging, has occurred. Funding from NGOs is often unreliable and stops before it can replace income lost when communities are no longer allowed to log. Mexican farming communities usually rely on local leaders, not the federal government, for guidance. Changes in land use caused by government and foreign policies have made the reserve less effective at protecting the environment and harmed local communities in the Oyamel mountains.

In her 2021 article, Gonzalez-Duarte uses historical and cultural information to explain how market-based policies by large international NGOs have affected Indigenous lands. She describes the long and difficult history of the reserve. When private and public groups became involved in the late 20th century, the land changed from being owned by communities to being controlled by private and state groups. This shift created a situation where land was taken in the name of protecting ecosystems, but it also helped expand capitalist interests and class advantages. It also allowed market-based systems to grow through financial changes and less government control.

Gonzalez-Duarte says that the UNESCO program and market-based systems in Mexico and North America have changed how people and nature interact, leading to more illegal activities and violence in the Oyamel Forest. The reserve’s boundaries have created a division between humans and nature, changing how authority is managed. These borders have become areas where market-based systems and governments allow violence to be carried out by outside groups to support illegal activities.

Organized crime in the Monarch Reserve has harmed the region and its people, making it harder for the area to thrive. Gonzalez-Duarte notes that the UNESCO Man and the Biosphere Program (MAB) has accidentally made it more likely that both people and butterflies in the reserve will disappear. To fix this, she suggests using traditional ecological methods that focus on balance between humans and nature to improve conservation for everyone.