Mangroves & Migration

Figure 1:  The edge of a dense mangrove habitat where it meets an open body of water 

Mangroves comprise a significant portion of coastal wetlands in tropical regions around the world. Thriving at the intersection of terrestrial forests, freshwater wetlands, and marine habitats, mangrove forests have a remarkable resilience to environmental change and disturbance (Alongi 2015; Bolívar-Anillo et al. 2019). As with many coastal wetlands, mangroves play the important role of protecting the coast from extreme events such as tsunamis, storm surges, and heavy rainfall from monsoons or hurricanes (Alongi 2015; Osland et al. 2015). Additionally, these ecosystems have an incredible capacity to store CO2 and other greenhouse gases (known as “carbon sinks”), with some of the highest rates of soil carbon density in the world (Osland et al. 2015; GFW 2018).

With eight mangrove species and over 200,000 ha of land area, mangrove forests along Colombia’s Pacific coast have been and still are among the most expansive and biodiverse in the Western Hemisphere (Bolívar-Anillo et al. 2019; Castellanos-Galindo et al. 2015; López-Angarita et al. 2016). As such, they serve as a valuable natural resource for Colombia’s economy and a prominent symbol of national heritage for its people. Colombia’s Pacific coast is a vast region, spanning four of Colombia’s departments, but it is not very densely populated, with Buenaventura the only major city. Even still, a significant presence of industry, agriculture, and other forms of natural resource exploitation dates back for hundreds of years (Castellanos-Galindo et al. 2015; López-Angarita et al. 2016).

With the onset of climate change, mangrove ecosystems along the Pacific coast will likely become more vulnerable, shrinking in their extent and declining in ecological functionality while migrating north in their range (Alongi 2015). The destruction and over-exploitation of mangrove forests will combine with the effects of climate change, worsening the ecological degradation already occurring in this region. Assuming mangrove destruction and resource depletion continue in the face of climate change, this phenomenon could not only cause strain on resource availability in Colombia and its neighboring countries, but it could also expose large coastal and inland cities to rising sea levels and more severe storms and force mass migration inland.

Mangrove forests long have served as a valuable natural resource to the inhabitants of Colombia, from hunter-gatherers as early as 700 BCE to Spanish settlers and other pre-Colombian societies, who intensified the exploitation of charcoal, fish, and (chiefly) timber starting in the 16th and 17th centuries (López-Angarita et al. 2016). From that point up through the mid-20th century, these extractive practices continued to rise, with mangrove timber harvesting and mining prevailing above all else (Castellanos-Galindo et al. 2015; López-Angarita et al. 2016). When timber production peaked at in the 1960s, mangrove degradation and destruction peaked as well due to land clearing for agriculture and coastal development and the spraying of DDT to combat tropical diseases (Castellanos-Galindo et al. 2015; López-Angarita et al. 2016). 

While timber production collapsed in the 1970s and conservation began to gain popularity in the 1990s, many sources of degradation have persisted into the 21st century. In recent decades, deforestation in this region has primarily been due to aquaculture (e.g. shrimp farming), agriculture (including illicit crop cultivation), urban development, and a revival of mining. In addition to deforestation, mangrove ecosystems face threats in the form of solid waste disposal, rising sea levels (among other effects of climate change), oil and gas exploration, and overfishing (Castellanos-Galindo et al. 2015; López-Angarita et al. 2016; Ramirez 2016). 

There are currently estimated to be between 200,000 and 300,000 ha of mangrove forest remaining along Colombia’s Pacific coast (likely much closer to 200,000), which is a 57% reduction even from peak industrial levels in the 1960s (Castellanos-Galindo et al. 2015; López-Angarita et al. 2016). According to López-Angarita et al., their estimated area in 2011 was 213,857 ha compared to 501,300 in 1960. The map above represents a small portion of this destruction, as country-wide destruction data only exists as far back as 1996. Green represents the total area where mangroves are present, with red showing destruction and blue showing regrowth in the past 20 years. Since satellite imaging and advanced geospatial technology have only been widespread over the past several decades, pre-1960 estimates are rough at best. However, given the well-documented history of deforestation and over-exploitation in the region over the past 400 years, it can be safely assumed that mangrove forests in 1960 were significantly smaller than that of the pre-colonial era.

Globally, mangrove forests are extremely resilient ecosystems that can act as indicators of environmental change given their unique position. They are shaped by multiple types of neighboring ecosystems, including terrestrial forests, freshwater wetlands, salt marshes, and marine environments, and thus the organisms that inhabit them are adept to harsh and highly variable conditions (Alongi 2015). Climate change will continue to worsen while these harsh conditions persist, but because they are so resilient, the effects on tropical mangrove forests themselves (including those in Colombia) will likely be complex and not purely destructive (Alongi 2015).

Among the greatest impacts posed by climate change are geographic shifts, which will occur multiple dimensions. Tropical mangroves are expected to shift away from the equator, with those in the Colombian Pacific moving north. This is mainly driven by rising ocean and air temperatures, although changes in rainfall patterns and chemical composition of the ocean may sometimes contribute as well (Alongi 2015; Osland et al. 2015). One harmful aspect of this northern range shift is the movement into neighboring wetlands in the Caribbean and Central and North America, where those wetlands will be displaced. However, the effects on migrating mangrove forests will be less straight-forward. They will most likely tolerate movement into freshwater environments, but migration northward may also present drier climates in which they will suffer. Overall, despite these variable situations, the extent of mangrove forests in Colombia is predicted to shrink as they shift north, with negative repercussions overall (Alongi 2015). 

In addition to increasing temperatures, rising sea levels and changing rainfall regimes have the potential to inundate mangrove ecosystems with salt water, forcing them to shift inland if space is available. In some areas, mangroves have been able to keep pace with sea level rise and endure water-logging, but in others, these changes are happening faster than mangroves can tolerate. Additionally, coastal development can hinder their ability to shift inland, further constraining their habitable zone or that of the ecosystem they are displacing (Alongi 2015; Osland et al. 2015). Therefore, these inland shifts may have variable effects on mangroves themselves, but infrastructure development is restricting their migration, and this movement will have mainly negative repercussions.

Because of their key coastal position, climate change will undermine the ecological stability of mangroves. Ocean acidification, warmer temperatures, and more intense storms will be imposed directly on them, creating a more hostile physical environment and testing the limits of these generally resilient environments. At the same time, sea level rise will inundate them with increasing amounts of saltwater from their neighboring marine environments, and in certain cases, waterlog them beyond tolerable levels (Alongi 2015; Osland et al 2015). Along with direct human deforestation, these effects destroy critical buffer zones, which provide protection from the impacts of climate change in the first place. 

Mangrove deforestation also removes vast amounts of carbon storage capacity. Known as “carbon sinks,” the soil and plants in many ecosystems have the ability to store large quantities of carbon dioxide and other greenhouse gases. Mangrove forests consistently contain approximately 300-400 Mg C/ha,* which is virtually unparalleled by any other ecosystem, making them among the most dense carbon sinks in the world. A conservative estimate (assuming a minimum of 300 Mg C/ha on average over 300,000 ha) would indicate that since 1960, approximately 90 million metric tons of carbon storage capacity have been lost in this region alone (López-Angarita et al. 2016; GFW 2018). For perspective, that is more than the annual CO2 emissions for all of Colombia (Global Carbon Atlas 2018). This consequence exacerbates climate change on both ends, fueling global warming by releasing greenhouse gases into the atmosphere while reducing the natural capacity to sequester those greenhouse gases.

*Megagrams (or metric tons) of carbon per hectare (10,000 square meters)

In terms of direct human degradation, mangrove deforestation is a major element in ecosystem loss and degradation, as much of Colombia’s Pacific coast has been subject to a total of 300,000 ha of clearance or modification for gold and platinum mining, agriculture (coconut, palm oil, and illicit crop cultivation), fish and shrimp aquaculture, oil and gas drilling, and coastal development (Castellanos-Galindo et al. 2015; López-Angarita et al. 2016). Additionally, decades of intense pollution threaten the stability of remaining ecosystems. Overall, these impacts will result in major biodiversity loss and population decline, reductions in ecosystem services, contraction in mangrove extent, encroachment into northern ecosystems, and diminished ecological resilience and complexity (Alongi 2015; López-Angarita et al. 2016; Osland et al. 2015). 

Given the socioeconomic marginalization of the Afro-Colombian population the comprises much of the population along the Pacific coast, as well as the political and economic unrest that pervades much of the country, Colombia is in a particularly sensitive position (Baptiste et al. 2017; Castellanos-Galindo et al. 2015). In addition to the extreme vulnerability of coastal cities like Buenaventura to sea level rise among other impacts of climate change, even some of Colombia’s farther inland cities such as Medellín and Cali may become subject to harsher impacts due to diminishing coastal buffers and strengthening storms. Thus, because climate change will disproportionately harm lower income and coastal populations, millions of people in some of Colombia’s largest cities are particularly vulnerable. 

Colombia’s Pacific coast has historically been incredibly productive, so a decline in resource availability and economic output from the region (which will be discussed further in the following section) would likely cause socioeconomic ripples throughout Colombia (Ramirez 2016). Goods such as fish, coffee, and tropical fruits are not only major exports produced largely on or near the Pacific coast, but they are also integral parts of Colombia’s rich culture. Similarly, the Pacific coast and the mangroves it hosts have societal value to the Colombian people as a source of unique foods, natural resources, and cultural practices, and its degradation comes a toll to the country’s cultural fabric. If not taken seriously and effectively mitigated, these amplified effects of climate change have the potential to further constrain resources, unravel social resilience, and deepen socioeconomic inequality (López-Angarita et al. 2016; Ramirez 2016).

Given the aforementioned biodiversity loss, ecosystem degradation, and increasing environmental hostility due to climate change, the Pacific coast is likely to become less productive, posing a major threat to Colombia’s economic output. Sectors such as fishing, shrimp aquaculture, mining, and logging (counting the large part of those industries which are illegal) are all widespread in the region and make up a significant portion of Colombia’s GDP (López-Angarita et al. 2016). Considering the high dependence those industries have on the region's natural capital, the ever-magnifying resource depletion and ecosystem collapse will undoubtedly have adverse effects on the output of this region. 

While these changes could force a transition toward more sustainable land use, development, and resource management, it might be too late to act. The window to enact meaningful mitigative and adaptive solutions to climate change is quickly closing, and many coastal communities are already on trajectory to experience devastating repercussions (López-Angarita et al. 2016; Ramirez 2016). Furthermore, future migration, reconstruction, and adaptation in the wake of climate change come at tremendous cost, as with many countries around the world (IPCC 2019). 

In order to avoid the worst and most irreversible effects of climate change, substantial action must be taken to practice more sustainable development and resource management as well as enact robust and widespread conservation efforts. In addition to adapting urban and industrial development, one of the simplest and most cost-effective solutions is to conserve existing mangroves and coastal wetlands and allow degraded areas to regrow. In order to carry out robust conservation efforts, however, the current state of conservation in Colombia must be acknowledged in order to improve it. 

While recent conservation efforts have been fairly successful in establishing protected areas in coastal regions, many have been implemented primarily due to international treaties and diplomatic pressure, and they often lack the oversight and enforcement necessary to be effective. In order to enact more meaningful and widespread protections for mangroves, there must be greater collaboration between communities, NGOs, and governments on all levels (Ramirez 2016). This will ensure that the interests of all parties involved are considered, conservation efforts can draw on a variety of groups for their unique strengths, and the protection of coastal areas can be governed and enforced as effectively as possible. As such, successful collaboration on the conservation of mangroves along Colombia’s Pacific coast will create a stronger coastal buffer against extreme weather events, slow the advance of climate change through enhanced carbon sequestration, and preserve the natural resources that Colombia both relies on economically and treasures as a cultural symbol.

Alongi, D. M. (2015). The Impact of Climate Change on Mangrove Forests. Springer: Current Climate Change Reports, 1(1), 30-39.

Baptiste, B. L. G. et al. (2017). Greening Peace in Colombia. Nature Ecology & Evolution, 1(2017), Article #0102

Bolívar-Anillo, H. J. et al. (2019). An Overview on Mangrove Forests Distribution in Colombia: an Ecosystem at Risk. Journal of Aquatic Science and Marine Biology, 2(1), 16-18. 

Castellanos-Galindo, G. A. (2015). Threats to mangrove social-ecological systems in the most luxuriant coastal forests of the Neotropics. Springer: Biodiversity and Conservation, 24(2015), 701-704

Global Forest Watch (GFW) (n.d.). World Resource Institute.  https://www.globalforestwatch.org/map/ 

Global Carbon Atlas - CO2 Emissions (2018) Global Carbon Project.   http://www.globalcarbonatlas.org/en/CO2-emissions 

The Intergovernmental Panel on Climate Change (IPCC). (2019). IPCC Special Report on the Ocean and Cryosphere in a Changing Climate; Chapter 5: Changing Ocean, Marine Ecosystems, and Dependent Communities. 

López-Angarita, J. et al. (2016). Mangroves and people: Lessons from a history of use and abuse in four Latin American countries. Elsevier: Forest Ecology & Management, 368(2016), 151-162

Osland, M. J. et al. (2015). Beyond just sea-level rise: considering macroclimatic drivers within coastal wetland vulnerability assessments to climate change. Global Change Biology, 22(2016), 1-11. 

Ramirez, L. F. (2016). Marine protected areas in Colombia: Advances in conservation and barriers for effective governance. Elsevier: Ocean & Coastal Management, 125(2016), 49-62.

Figure 1: Mangrove edge habitat - photograph by Nicolas Moity:  https://medium.com/google-earth/documenting-mangrove-forests-in-the-gal%C3%A1pagos-islands-with-help-from-google-earth-50e7f10d4262 

Figure 2: Mangrove presence along Colombia's Pacific Coast - Global Forest Watch:  https://www.globalforestwatch.org/map 

Figure 3: Pesticide spraying over forest - no photographer listed:  https://en.wikipedia.org/wiki/Operation_Ranch_Hand 

Figure 4: Mangrove Timber - no photographer listed:  http://www.mangrove.at/rhizophora-mangle_red-mangrove.html 

Figure 5: Port of Buenaventura - photograph by Maria Quintero:  https://www.shutterstock.com/video/clip-25799441-aerial-port-city-buenaventura-colombia 

Figure 6: Mangrove loss south of Buenaventura - 1996-2016 - Global Forest Watch:  https://www.globalforestwatch.org/map 

Figure 7: Coastal flooding in Chocó - photograph by  Tostao :  https://colombiareports.com/west-colombia-suffers-while-duque-is-busy-with-venezuela/ 

Figure 8: Coral reef bleaching due to rising ocean temperatures - photograph by XL Catlin Seaview Survey:  https://www.marineconservation.org.au/coral-bleaching/ 

Figure 9: Map of geographic shifts mangroves will undergo with climate change - labels added by author; Map from Global Forest Watch:  https://www.globalforestwatch.org/map 

Figure 10: Annual Average Temperature Change in Colombia - World Bank Group, Climate Change Knowledge Portal:  https://climateknowledgeportal.worldbank.org/download-data 

Figure 11: Forest along Colombia's Pacific coast - no photographer listed:  https://www.galavanta.com/destinations-pacific-coast/ 

Figure 12: Mangrove Deforestation - photograph by Oliver S.:  https://www.carbonbrief.org/mangrove-deforestation-emits-as-much-co2-as-myanmar-each-year 

Figure 13: Importance of Mangrove Forests - Mangrove Action Project:  https://www.youtube.com/channel/UCKyF_x7Zre-vsLHXTVDK5QQ 

Figure 14: Map of soil carbon density along the coast south of Buenaventura - Global Forest Watch:  https://www.globalforestwatch.org/map 

Figure 15: Cali - no photographer listed:  http://brandlab.americaeconomia.com/innovacion-salud/p/1 

Figure 16: Afro-Colombian women in Cartegena - photograph by Luz Adriana:  https://theculturetrip.com/south-america/colombia/articles/a-brief-history-of-san-basilio-de-palenque-cartagena/ 

Figure 17: Colombia's Coffee Region - photograph by Chris Bell:  https://theculturetrip.com/south-america/colombia/articles/the-8-best-coffee-experiences-in-colombia/ 

Figure 18: Surging Seas Sea Level Rise Map - Climate Central:  https://seeing.climatecentral.org/#13/3.8703/-77.0408?show=lockinAnimated&level=0&unit=feet&pois=hide 

Figure 19: Skyline of Bogotá - photograph by Peter Liévano:  http://www.peterlievano.com/tag/bogota-skyline /

Figure 20: Colombia's GDP by Sector in 2017 - Wikipedia:  https://en.wikipedia.org/wiki/Economy_of_Colombia 

Figure 21: Map of protected areas along the Pacific coast - Global Forest Watch:  https://www.globalforestwatch.org/map