Agriculture is decreasing carbon stocks in the Ecuadorian páramo

Environment | Mountains

By Julia Riopelle, Co-Editor in Chief

Published January 24th, 2022

The Andean Páramo has a uniquely high soil carbon storage potential, which contributes to the water retention and hydraulic conductivity that are central to providing fresh water to its surrounding communities. However, studies are suggesting that the impact of expanding agriculture is steadily depleting the soil from its carbon levels.

The páramo is an alpine tundra ecosystem located in the Andes Mountain Range, home to high biodiversity and plant endemism (i.e plants only found in that region). Its vegetation is above the continuous forest line in the mountains and below the permanent snowline, at an altitude between 3,000 to 5,000 metres.

The Andean páramo near Quito, Ecuador. | Andres Medina / Unsplash

According to Christmann et al. (2020), the vegetation of the páramo is at least four million years old—its long history giving rise to 30 endemic genera. The lower temperatures and humidity of Ecuadorian páramo, specifically, is home to unique daisy (Compositae) and grass (Poaceae) families.

There are two key features that make the páramo unique to others; its high carbon storage capacity and its hydrological system, allowing for efficient water retention, storage and provisioning. Carbon levels in the Northern Andes páramo have been measured at 2,100 megagrams of carbon per hectare, which is one of the highest levels in mountain ecosystems. The cool temperatures of this region slow down decomposition, which in turn increases the carbon storage capacity of its soils.

At a one metre depth, the carbon levels in Quito, the capital of Ecuador, were an average of 561 megagrams of carbon per hectare. When comparing this to the 59 to 299 megagrams of carbon per hectare in the Spanish Pyrenees, 40 to 220 megagrams of carbon per hectare in the Rocky Mountains and 115 to 498 megagrams of carbon per hectare in the Scottish highlands, one can recognise the importance of Andean páramo ecosystem as a carbon sink.

Ten million people live in the Northern Andean páramo, however, new socio-economic and political influences have driven land-use change throughout this ecosystem. The Ecuadorian páramo—specifically, three-quarters of it—has experienced more of this change than those in Venezuela and Colombia, decreasing by 0.8% in area per year between 1963 and 1991. This is primarily due to expansions in agricultural areas and land for grazing livestock.

‘The Ecuadorian páramo has decreased by 0.8% per year between 1963 and 1991.’

Although the páramo ecosystem covers 5% of the land area in Ecuador, only 40% of this land is under protection. The land that is not protected is being degraded due to soil erosion, changes in land-use policy, deforestation, urbanisation and human migration patterns.

A study looking at Río Chambo Basin, which is located in the centre of Ecuador, found that by 1991, 18% of the páramo surrounding the Basin was converted for agricultural purposes. The crops above 3,500 metres are dominated by the growth of potatoes and other staple tubers.

Additionally, researchers Ross and Fildes (2017) state that ‘forest plantations had replaced a further 994 hectares, and 312 hectares of bare soil and rock had been exposed by erosion, recently cleared prior to cultivation or had been built on.’

Approximately 70% of rural inhabitants directly rely on the páramo around Río Chambo Basin for food, timber, drinking water, irrigation and more. The páramo is also closely tied with their cultural identity; though their traditional ways continue to be encroached by modernization and new development plans.

Rural landscape near Quito, Ecuador. | A. Davey / Flickr

Overall, Ross and Fildes (2017) conclude that three-quarters of the páramo region around the Chambo Basin remained unchanged in their 30-year study period between 1979 to 2014. They state that, ‘the major land‐use and land‐cover transitions in the Chambo basin have similarities with those in Pambamarca, where the main pathways were from páramo to farmland, bare ground and grazing; and bare ground to farmland.’

However, the effects of land-use change have hit other parts of Ecuador to a further extent, and their implications are evident. A recently published study by Thompson et al. (2021) found that near Ecuador's capital, Quito, the agricultural land within their study area increased from 4.45% to 11.32% between 1991 to 2017, with agricultural land-use change projected to rapidly increase in the next 26 years.

The high carbon levels in páramo soil allow for higher water retention and hydraulic conductivity, however, agricultural practices that change this soil chemistry have caused previously unknown rates of carbon storage loss.

‘Agricultural land within their study area increased from 4.45% to 11.32% between 1991 to 2017.’

Thompson’s study revealed how land-use change is affecting the carbon sequestration levels of páramo soils. The study took place within a nature reserve, between 3,500 to 5,000 metres above sea level, and the soil there provides most of the water for the city. Using a deep soil core, the team sampled soils from various land types—crop, pasture, fallow and ‘natural’ grids—in order to compare their carbon levels.

Thompson and her team found that the carbon levels at the sites ranged from 239 to 2,778 megagrams of carbon per hectare, with a mean of 1,418 megagrams of carbon per hectare across all land types. Their findings also inferred that initial cultivation of land would cause a decrease in carbon storage, although only within the first 10 centimetres of soil depth, as it was only here that natural plots had the highest percentage of carbon content.

They linked the decreased carbon levels to agriculture practises, such as tilling, as cultivated plots had the lowest percentage of carbon content compared to all other land types. Tillage increases erosion and decreases water infiltration rates, thus reducing the ability for water to collect in subsurface catchments. In turn, reducing tillage can decrease soil exposure to the air and prevent carbon from being released back into the atmosphere.

Chuquiraga jussieui, flower of the Andes. | Anita Gould / Flickr

Thompson J. (2021): ‘Páramo ecosystems account for less than 1% of the total land in Venezuela, Colombia, Peru, and Ecuador, yet millions of people from these countries depend on páramo ecosystems for the provision of water for human consumption and sanitation, and large portions of their economy rely on that same water supply for irrigation and generation of energy.’

However, now with an estimated absolute loss of 0.045% of soil carbon per year due to agricultural use, equivalent to a 28% decrease in soil carbon over fifty years, the particular chemistry of páramo ecosystems may be increasingly threatened. The team’s projections of carbon loss may be conservative, as they did not measure carbon loss directly related to erosion.

Not only is land-use change affecting the ecosystem’s ability to sequester carbon dioxide, but also its ability to hold underground water—affecting those Andean communities who rely on the páramo as a primary water source. Additionally, decreasing levels of soil carbon over the coming decades will impact the vegetation and animals which rely on these soil conditions—a unique ecosystem that took four million years to evolve.

Featured Image: Dr. Alexey Yakovlev | Flickr

Christmann T. and Oliveras I. (2020) Nature of Alpine Ecosystems in Tropical Mountains of South America. Encyclopaedia of the World's Biomes. Volume 1, pages 282-291.

García V., Márquez C., Rodríguez M., et al. (2020) Páramo Ecosystems in Ecuador’s Southern Region: Conservation State and Restoration. Agronomy. Volume 10, issue 1992.

Ross C., Fildes S., Millington A. (2017) Land-Use and Land-Cover Change in the Páramo of South-Central Ecuador, 1979–2014. Land. Volume 6, issue 46.

Thompson J., Zurita-Arthos L., Müller F., Chimbolema S. and Suárez E. (2021) Land use change in the Ecuadorian páramo: The impact of expanding agriculture on soil carbon storage. Arctic, Antarctic and Alpine Research. Volume 52, number 1, pages 48-59.

Southeast Asia’s mountains are losing their tropical forests to make room for agricultural expansion

Environment | Mountains

Sub-Saharan groundwater supply in the face of climate change—an uncertain future?

Environment | Deserts