Climate change in Mexico

Climate change is a critical concern in Mexico, particularly in relation to agriculture. Drying and warming trends are altering and shifting climatic zones and agricultural environments worldwide,[22][23] and Mexico is no exception.[22] According to the World Bank, “agriculture [in Mexico] is highly vulnerable to weather extremes, in particular in the Northern parts of the country, where water scarcity is an issue, or the Southern parts of the country, where tropical storms cause extensive damage to crop[s].” [24][17]

Exact predictions are difficult to make due to the complexity of the factors involved and the impacts will be highly region-specific; however, there is a general consensus that the productivity of crops and livestock will decline.[25] Scientists also expect that certain insect pests and plant pathogens will survive and reproduce more often due to warming temperatures and are likely to invade new regions.[26] Highland farmers and the rural poor are especially vulnerable to these climatic shifts.[22] Decreased precipitation will place higher burdens on irrigated agriculture, on which much of the country’s exported, economically-important crops rely.[27] Conversely, more intense rainfall events will damage crop production. Higher temperatures are expected to increase evapotranspiration rates, leading to drying trends in soil moisture.[27]

"Wheat production for Mexico is expected to decline by 12% under the future RCP 8.5 climate change scenario with additional losses of 7 to 18% because of O3 impact," according to a July 2019 article.[28] In the Yucatán Peninsula, the rise in temperature is affecting crop production.[1] Extreme heat can negatively affect crops by slowing down growth and increasing moisture loss in the soil.[29] Over the past 15 years until 2010, a Mayan village in Cancun, Tabi, experienced a 50-60% reduction in crop yield. Additionally, climate change is affecting rainfall patterns. Farmers are finding it more difficult to predict rainfall, which if predicted wrong can waste "an entire season's worth of seeds".[30]

Declining agricultural conditions due to climate change has impacted farmer livelihoods in varying ways.

Climate change has caused many people in Mexico who depend on agriculture for employment to experience economic insecurity. In 2017, an estimated seven million people were employed in the agricultural sector in Mexico.[31] Moreover, many Mexican smallholder farmers continue to depend on rain-fed agriculture for their subsistence and livelihoods.[27]

Climate change is very closely tied to environmental justice in Mexico, given that poor smallholder farmers will likely carry the largest burden[32]. Farmers respond to climate change in varying ways: changing their agricultural practices, adjusting their livelihood strategies, or exiting agriculture altogether.[22]

There is evidence to suggest that declining agricultural conditions from climate change in Mexico directly relates to migration to the United States.[33][20] For example, Feng et al. (2010) found a direct relationship between declining crop yields in Mexico and migration[33]. Using the results from their analysis, they projected that declines in agricultural productivity due to climate change will cause 1.4 to 6.7 million adult Mexicans to emigrate by the year 2080[33]

Maize, a key component of Mexican agriculture, is threatened due to temperature and precipitation fluxes from climate change

Climate change threatens not only food and economic security in Mexico, but is also tied to much larger, global food systems. In 2017, the United States imported $13.3 billion of fruits and vegetables from Mexico.[31] Declining crop yields in Mexico due to climate change will ultimately impact global trade networks, national economies, and food security in countries that are, perhaps, geographically distant; yet through free-trade policies such as NAFTA and USMCA, have become highly dependent on Mexican agriculture.

The Mexican government’s climate change program explicitly identifies “the adoption and implementation of sustainable agriculture” as a key adaptation strategy[17]. Sustainable agriculture can take many forms. One type of strategy that has been proposed includes changing farmers’ agricultural practices. For example, changing the timing of irrigation and crop planting, introducing new landraces and cultivars by extending seed-sharing networks, and adopting biodiversity friendly farming practices that increase agroecosystem resilience[17]. Evidence suggests that smallholder farmers in southern Mexico have begun adapting their agricultural practices due to climate change, by, for example, delaying crop plantings and planting a diversity of landrace varieties[17].

Another strategy focuses on the development and promotion of new, transgenic, “climate-adapted” seed varieties that have traits for drought- and disease-resistance[17]. Researchers have also noted the importance of state leadership in addressing climate change by, for example, training and preparing farmers for climate adaptation[17]. However, implementation of any adaptation or mitigation strategy will need to take into account the complexity of coupled human-natural systems, wealth and power inequities, and the varying scales at which climate change processes are occurring[34][17].

Maize and coffee are particularly important crops to the Mexican agricultural system. They both are expected to have severe impacts.

Maize is of central importance to Mexican agriculture, occupying the largest cultivated area in the country.[22] It is a critical component of the diets and nutritional intake of both the urban and rural populations. A large number of smallholder farmers in Mexico depend on rain-fed maize for their livelihoods, leaving these farmers particularly vulnerable to temperature and precipitation fluxes from climate change.[22] Mexico’s maize yields are expected to decline from 1555 to 1440 kg/ha by 2055[35]. An absolute decline of 883,200 t. in maize annual production is estimated to occur within this timeframe[35] Maize is closely tied to Mexican identity, thus any decline in maize productivity and diversity will also have important socio-cultural and political consequences[32][17].

Mexico (Mesoamerica more generally) is the center of origin for maize. Mexico alone has 59 unique maize landraces recorded[36] and thousands of regionally adapted maize varieties. Maize diversity in Mexico continues to be maintained and managed by smallholder farmers who participate in traditional seed sharing networks. Maize landraces in Mexico are conserved in place, or in-situ, by farmers who continue to grow them in their fields. Commercial maize seed is planted on less than one-fourth of Mexico’s 8 million hectares of arable land[17]. The majority of farmers in Mexico use, save, and exchange the seed of traditional maize landraces along with “creolized” (hybridized or cross-pollinated) commercial cultivars, which are typically planted in small (<5 ha) rain-fed fields[17].

An estimated 18 percent of maize cultivation in Mexico takes place in the highlands, and maize agro-climates in the highland regions are most at risk from climate change.[22] Many scientists are concerned about the effects climate change poses on maize genetic diversity and the negative impacts that continued maize germplasm loss will have, not only on Mexican agriculture, but worldwide, as maize is the most widely grown crop in the world.[36] Bellon et al. (2011) discuss the need to strengthen and broaden traditional seed networks in Mexico to support farmers and the genetic integrity of maize in light of climate change; thus, extending the geographic ranges of seed networks to link farmers in the highlands, for example, with farmers in mid-altitude environments.[22]

Due to a continual process of farmer-mediated selection and their diverse genetic makeup, maize landraces in Mexico have the ability to adapt and evolve to changing environmental conditions; although it will be difficult to predict exactly how they will change or the extent to which they will be able to adapt, particularly to rising temperatures[22][17]. Biotechnology, and the development and promotion of maize transgenics in particular, is being promoted as a critical climate adaptation strategy, not only in Mexico but around the world. While stress-tolerant maize transgenics could bring important benefits to Mexico, there are a number of concerns associated with them. In particular, concerns have been raised about the lower productivity of improved varieties compared to landraces in many parts of Mexico[37]; the longstanding lack of acceptance of transgenic varieties by Mexican farmers[17]; and that the promotion of transgenics threatens local landrace diversity[38][17]. Participatory maize breeding, that is the inclusion of farmers in the formal breeding process, may hold considerable potential for climate change adaptation in Mexico[17].

Coffee produced in Mexico.

Variable and extreme climatic events such as droughts, floods, and excessive heat will have – and is already having - important impacts on both the quality and overall production of coffee in Mexico.[20] In Mexico and Central America more broadly, some 8.5 million people rely on coffee production for their livelihoods.[15] In 2012, higher than average temperatures and high-altitude rains led to an outbreak of coffee leaf rust, affecting roughly 50 percent of the coffee crop in Central America.[15] This resulted in $500 million in crop damages to the region and caused many people in the region to lose their livelihoods.[15] Regional studies in Mexico have projected that coffee growing could be unviable by the end of the decade.[20] Responses will need to occur both in the social and ecological realms and across multiple scales. Key strategies include crop diversification and the implementation of more resilient coffee production systems. Farmer education, access to information, health, and equity factors all play important roles in adaptation responses as well.[20][15] Yet, there are also large-scale and global factors at play, such as international trade markets, which are often volatile, that are beyond farmers’ control. A handful of coffee companies, NGOs, and agencies have initiated training and education programs for Mexican farmers to better respond to climate change.[15]

Recommended climate adaptation strategies for coffee production in Mexico include (1) promoting farming practices that increase biodiversity, such as agroforestry, which provides protection against extreme weather events and allows for product diversification, (2) diversifying farmer incomes to mitigate risks from climate and market volatility, and (3) enabling markets that support sustainable coffee growing practices, among others[39]. Shade-grown coffee (typically with Coffea arabica in Mexico) provisions critical ecosystem services: pollination and hydrological services, wildlife habitat, and pest and erosion control[39]. It has been estimated that 60-70% of coffee production in Mexico is grown under shade by a diversity of tree species[40]. However, there is concern that hotter growing conditions and irregular rainfall patterns will cause a decline in coffee quality and hence profitability, propelling farmers to abandon shade-grown coffee altogether[39].

Much of Mexico's coffee (Coffee arabica) production is grown under the shade of a diversity of tree species. There is concern that climate change will lead to a decline in coffee quality, potentially causing farmers to abandon biodiversity friendly agroforestry practices.

Image depicting global cloud forest distributions.

Mountain cloud forests, especially in the Michoacán, act as dispersal corridors for many species that travel between habitats.[41] These forests are highly subject to human disturbances such as mining and deforestation.[41] This is important because the distribution of these forests is an integral factor of landscape connectivity.[41] As the distribution of these forests changes due to climate effects, landscape connectivity is also affected.[41] An evaluation of this property of connectivity of the mountain cloud forests of Michoacán was carried out by researchers in order to determine which areas would best benefit from greater conservation efforts.[41]

Warming temperatures and land-use change are contributing to the movement of butterfly distributions up the Sierra de Juárez mountain range in Oaxaca, Mexico.[42] In 2016, research was conducted to determine which butterfly species were moving either up or down the mountain range.[42] The researchers determined that more species were moving upward than were moving downward.[42] The researchers also concluded that, as a result of distribution changes, there was a greater abundance of generalist butterfly species in lowlands.[42]

Mexican Free-Tailed Bats: As a result of climate change, bat ranges in Mexico are shifting due to declining habitat suitability.

Bat distributions and ranges in Mexico are expected to shift as a result of changes in climate and increased land-use change.[43] As an indicator species, bats can provide researchers useful information in regard to the degree and extent of climate related species responses.[43] Researchers analyzed previous records of bat occurrence across Mexico and used the derived data to project how bat species may respond to land-use change and climate effects.[43] Results showed that habitat suitability for over half of 130 bat species is expected to decrease under current climate trends.[43] The results also revealed that land-use change had less of an effect on habitat suitability for bats than climate change.[43]

Photograph of a dry forest within the Chamela-Cuixmala Biosphere Reserve.

A significant number of mammals are endemic to Mexico, an abundance of those species being small mammals.[44] Many of these small mammals are known to inhabit tropical areas of Mexico, however, it is these tropical dry ecosystems that are highly subject to the effects of land-use change and climate change, making small mammals particularly vulnerable.[44] Researchers set up a 19 year study of small mammal populations in the Chamela-Cuixmala Biosphere Reserve located in Jalisco, Mexico.[44] This site was chosen by the researchers due to the occurrence of a significant amount of anthropogenic disturbance in the surrounding area.[44] The researchers concluded that functional diversity in this area was lower than expected, and, as such, greater conservation efforts should be encouraged in the region.[44]

In order to determine how conservation efforts should be implemented in order to best protect breeding bird communities, a study was conducted by Aaron D. Flesch.[45] This study of breeding bird communities in Mexico found that species were trending higher in altitude and towards the poles.[45] In order to collect his data, Flesch used techniques that had been used by previous researchers and conducted an observational survey to determine biodiversity values.[45] From the collected data and historical climate data, Flesch found that some lowland species moved north and others moved east to higher altitudes.[45]

Mexico contains a significant portion of the world's biodiversity, making it essential that "biodiversity hot-spots" present within its borders are properly protected from the effects of climate change.[46] A large amount of land area in Mexico is already designated as protected areas, as such, these conservation areas make refugia for a number of threatened species.[46] Researchers are investigating how protected ecosystems in Mexico will be affected by climate change, and to what degree.[46] Their research concluded that all 40 of the studied protected areas are expected to face warming temperatures while 30 will face decreased precipitation.[46] The researchers suggest that their study be used to determine which of the protected areas in Mexico would benefit most from greater conservation efforts.[46]