Over the twentieth century, economic and population growth led to unprecedented levels in the appropriation and use of energy and materials worldwide [1
]. Although resources such as fossil fuels and other minerals dominated this increase, the appropriation of biomass has continued to grow. This is driven by increases in population along with incomes and dietary changes [2
]. This process has shaped the profile of fossil fuel-based agroecosystems [4
] increasing the environmental pressures on nature. The amount of nitrogenous fertilizers used in agriculture around the world has moved from 11 million to 109 million in the last half-century, which is a ten-fold increase [7
]. Global biomass extraction increased by 60% between 1980 and 2013 [8
], while the proportion of the world’s area being harvested increased by 40% from 1990 to 2014 [7
Pollution, soil erosion, the decline in biodiversity, and damage to human health and deforestation, especially of tropical rainforests [9
], are among the main consequences and challenges of industrial agriculture [11
]. However, despite the trilemma of challenges posed by the energy, environment, and food [12
], it is still possible to confront the environmental impacts of farming and the projected rise in the demand for food, feed, biofuel, and other biomass-based resources by increasing the efficiency of nutrients and water use, reducing waste, and changing diets, policies, and agricultural practices [3
]. Biomass is essential to the economy [16
], but it is also crucial to ecosystems and the functioning of the landscape. The cycling of biomass flows within agroecosystems plays a valuable role in promoting crop productivity, maintaining farm-associated biodiversity, and preserving underground life forms by restoring eroded soils and improving their organic matter content, fertility, and structure. Biomass is also a critical element in nutrient and carbon cycles [13
]. Therefore, the careful management of biomass flows is a key element along the path towards more sustainable forms of agriculture. To that end, a better understanding of the historical roots of the changes in biomass production, appropriation, and uses are essential to new agro-ecological forms of the management of biomass chains.
The most used approach when it comes to analyzing biomass flows at national scales is human appropriation of net primary production (HANPP) [19
], defined “as the aggregate human-based effect of land-use induced changes in productivity and biomass harvest on the energy availability in ecosystems” [22
] (p. 48). Although HANPP provides an assessment of human intervention in the biosphere, even in the long run [23
], it does not provide a detailed picture of Net Primary Production (NPP) chain flows, and the works focus mostly on Europe [24
]. In another way, material flow accounting (MFA) has become a standardized methodology for the study of the extraction and use of material flows, including biomass [25
]. Although MFA does not always account for biomass production in detail, ignores the belowground flows of biomass, and the biomass in circulation (see Section 2.1
for details), it is a useful tool for the studies at the national scale. MFA has been directly or indirectly used in several case studies such as in Spain [28
], Finland [29
], Czechoslovakia [31
], and even on a global scale [33
]. All these cases have relied on the MFA approach, but they all also provide additional indicators on production, use, or input consumption. However, none of these papers focus on developing economies, and just three of them provide a historical perspective.
In this paper, we present, for the first time, a long-term estimation of the biomass flows in a developing, tropical, American economy. There is new data on NPP, extraction and use of biomass from crops, pastures, and forest between 1915 and 2015 in Colombia. Our main goal is to provide a biophysical reading of agrarian change as well as to identify the timing and features of the (un)sustainability of farming carried out in Colombia during the period. Using new, detailed information, it analyzes changes in land use and biomass extraction to identify the critical points at which the agricultural sector may have constituted a burden to the ecosystems, which places the global periphery at the core of the debate over the agrarian socio-metabolic transition.
Colombia represents a fascinating case study within Latin America for the socio-metabolic study of biomass flows for several reasons. The country is representative of a medium-sized economy in the region. GDP (at current US$
) in the country in 2016 was around 282 billion, which is very close to Chile (247) and twice bigger than the GDP of Ecuador, Paraguay, Bolivia, and Uruguay, and half of the GDP of Argentina. Concerning the population, after Mexico, the country is the second largest with 48 million inhabitants. It is comparable to Argentina (43), Peru, and Venezuela (31) [35
]. Lastly, and more importantly, the country is the second largest biodiversity reservoir around the globe. Following the data from Biodiversity Information System in Colombia (SiB) [36
], the country occupies the first place in birds and orchids, the second in plants, amphibians, butterflies, the third in reptiles and palms, and the fourth in mammals. Biological variety is the result of the differences among its ecosystems, including tropical forest in the Amazon and Chocó, mountain ecosystems in the Andes, or grasslands and meadows in the East of the country [36
], which is why biodiversity loss in Colombia is a global issue. The study of the biomass flows during the twentieth century in Colombia places the socio-metabolic transition of an exporter country and a developing economy from Latin America into the framework of changes in western agriculture. The ecosystem variety and the differences between the tropical and Andean agriculture inside the country could be a benchmark for future research in the region. In addition, this kind of approach can contribute to a better understanding of the long-lasting violent political conflict in Colombia.
The remainder of the article is structured as follows. The second section explains the methodological approach, sources, and treatment of data. In the third section, we present the main series on land uses, NPP by types of land cover, the extraction and the uses of biomass, livestock figures, and crop yields. We attach the series of the NPP, extraction, and uses in the supplementary document. Lastly, we discuss the results in light of the main phases of the socio-metabolic transition and offer an initial exploration of the main drivers and the socio-ecological impacts of the changes in the composition of biomass flows.
3.1. Land Use Changes
Colombia’s land area is 110 Mha, the main cover being forests, with an average proportion of 54% between 2005 and 2015 (60.1 Mha average). However, at the beginning of the twentieth century, this figure was 68% (76.2 Mha), and it was consistently higher than 65% (72 Mha) until 1964 (see Figure 1
). The area under the forest fell from 76 to 59 Mha during the twentieth century. This average loss of 22% was more profound in the case of the Andean forest than in any other forest cover, especially since the 1970s, due to the historically higher population densities in this region [76
]. The share of the Andean forest over the total land area fell more than half, from 19% to 8%, during that period. The tropical dry forest has represented a tiny part of the whole forest area and, although its deforestation has slowed since the 1970s [76
], it is at risk of disappearing entirely [78
]. The rest of forest covers have stayed almost constant at around 12 Mha.
The categories of pasture and shrub land & others combined represent the second largest type of cover, which accounts, on average, for a third of the land area during the 1915 to 1984 period, but, by the mid-1970s, this figure rose and presently represents more than 40% of the total land area. Pasture and shrubland increased the area from 32.6 Mha in 1970 to 45 Mhas in 2015, but it is worth remembering that, in our series, the shrubland & others land use is a residual category whose fluctuations reflect the dynamics of the other types of land cover. However, it has some interesting features. Between 1915 and 1980, it fell from 21% (24.5 Mha) to 12% (13.2 Mha) due to the expansion of cropland and pastureland. After the 1980s, shrubland and others recovered and reached 19% (21 Mha) in 2014 while cropland stagnated and the growth in grass pasture slowed. At the beginning of the period, the pastureland represented only 8% (17.3 Mha) of total land area. It doubled during the 1970s and since the early 1990s covers more than 20% (24 Mha in 2015) of the total land area.
Lastly, although the area under cropping is only a small part of the total land area, its change is even more significant than that of pasture. The cropland experienced a four-fold increase between 1915 and 2015, which moved up from 0.9 Mha (1% of land area) to 5 Mha (4%) and reached its highest point in 1978, 6.9 Mha (6%). The process of cropland expansion was more intense during the first half of the century (1915–1964), with an annual rate of growth of 3.6% than during the second half (1965–2015), when the growth stagnated. The intensification of agrarian production under industrial management and increases in imports of staple food items are the main factors behind the stagnation of the agricultural frontier, which we will discuss below.
Regarding the area harvested by crops (Figure 2
), we can divide the frontier expansion into three sub-periods. In the first two periods, intensive ploughing is observed. From 1915 to 1944, the cropland annual growth was 4.5% and, from 1945 to 1974, it was 1.5%. However, after 1975, the agricultural frontier stagnated, with an average annual rate of growth of only 0.3% (Figure 2
By looking at crop compositions, we observe that staples have traditionally been the largest crop group. Their percentage over total cropland area has barely changed during the analyzed period, which moved from 55% to 43%. However, if we focus on cereals, we observe a sharper drop (Figure 2
b). Between 1915 and 1954, cereal crops occupied more than 40% of the area harvested. Afterwards, their share lost importance by up to 27%. From 1915 to 1960, the reduction in the proportion of arable land devoted to cereals was offset by the increase in the production of stimulants, especially coffee, which moved from 11% to 29%. However, the share of land under coffee plantations fell after that date and reached 20% of the cropland area in 2015. Fruit crops (both traditional and new ones) and oilseed crops have filled the gap left by the contraction in the cropland areas of coffee and cereals (see Figure 2
b). Among oilseeds, the oil-palm fruit stands out and has expanded since the late 1980s with a share of 8% of the total area harvested at present.
3.2. The Long-Term Trend in NPP
During the analyzed period, the NPP experienced a 10% reduction from 2 Gt in 1915 to 1.8 Gt in 2015 (Figure 3
). Between 1915 and 1994, the annual rate of change was, on average, −0.13%. However, after that year, it fell to −0.04%. In other words, although we observe a long-term pattern of decline in NPP, as of the 1990s it stagnated. Nevertheless, the volatility of the short-term variation of the NPP increased during the second half of the century. The standard deviation of the annual rates from 1915 to 1964 was 0.07%, but it more than doubled from 1965 to 2015 (Figure 3
The weight of the NPP in forest lands dominates the composition of the NPP. It comprised 80% of the whole NPP until 1974, but from 1975 to 2015, its share fell from 78% to 71%. However, there have been sharp disparities in the trend and composition of the different types of forest. The main component of the whole NPP in forest lands is rainforest, which is the most productive and the primary land cover in most of the country (see Figure 1
). Although its area has been reduced, its NPP contribution to the total has stayed almost constant at near 50% of total NPP. Conversely, the Andean forest reduced its NPP share by half, from 21% to 11%, which fell in absolute numbers from 434 to 184 Mt throughout the period.
The NPP of pastureland and shrub land, where there is also secondary vegetation, fell from 19% to 18% between 1915 and 1974. This slight reduction corresponds to the shrub land NPP falling from 22% to 13%, or from 487 to 298 Mt in absolute figures, and a rise in the pasture NPP from 3% to 7%. After 1975, the NPP figures for pastures and shrub land recovered somewhat, increasing from 11% to 15% of the total share. This increasing trend was opposite that for the forest, especially the 10% reduction in the Andean forest NPP. The pasture and shrub land NPPs rose by 0.75% during this period of growth. However, the major gains were achieved for shrub land. The increase in the pasture NPP mainly took place during the first period at an average annual rate of 1.6% between 1915 and 1974, when the shrub land NPP was falling, and did not occur during the second period.
Similar to pastures, but to a lesser extent, the share of the NPP in cropland rose from 0.2% in 1915 to 2% in 2015. Despite it having only a tiny share of total NPP, the increases in the NPP for crops were the most dynamic, even more than those for pasture, which means a nearly fifteen-fold increase from 3 to 44 Mt throughout the century. The average annual rate of growth in cropland NPP was 3% for the whole period. By grouping this increase in 10-year periods, the annual growth rates fell from 3% to 0.1%, and there are three different sub-periods. The 1915–1944 period saw the most exceptional period of growth at 4.5%. From 1945 to 1974, the growth rate experienced a slight reduction down to 3%, but then recovered from 1955 to 1964 by 4%. Lastly, there was a period of lower growth of around 2% between 1975 and 2015, which is followed by an apparent fall in the growth rate at the beginning of the 21st century (Figure 4
By groups of crops, the most basic division into arable and permanent crop production initially seems favorable to the second one. Staple food crops such as cereals, pulses, tubers, and vegetables shared on average 30% of NPP production in cropland during the whole century while cash crops like fruits, oilseed crops, fibers, stimulants, and sugar or sweeteners produced the other 70% (sd. 4.5). The first feature that stands out is the importance of sugar and sweeteners, with an average share of 50%. Although there are some variations during the period, the standard deviation is low (sd. 5). The most significant change is observed in the decreasing trend in the share of basic grains of 22% between 1915 and 1924, falling by up to 16% from 2005 to 2015, and a total drop during the analyzed period of 7%. The stimulants group, headed by coffee, also reduced its share from 8% to 2% between 1925 and 1934. Conversely, oilseed crops, mainly palm oil, increased their share from mid-century onwards and represent 7% from 1965 to 1974 and 17% from 2005 to 2015.
3.3. Final Uses of NPP Extraction
Domestic extraction (DE) of biomass increased nearly three-fold during the period. Meanwhile, total NPP fell by 10%. Consequently, the DE share of total produced phytomass increased from 1% to 6%. Of this total, the grassland experienced the most significant degree of extraction with a share of 70% on average throughout the whole 1915–2015 period. However, the share of grassland fell from 80–70% before the 1960s to 60% in the 2010s (Figure 5
a and Figure 7). The second largest extraction was of crops, which is a third of total DE in the last several years. In the long run, the categories in the second position of DE components experienced a switch. From 1915 to 1960, this position was occupied by forest extraction, but from 1970 onwards, the increasing trend in crop extraction surpassed the share of forestry. After this tipping point, forest extraction fell from 17% to 7% in 2015. This process was driven by the reduction in fuelwood consumption due to the energy transition to “modern” energy carriers, which are mainly fossil fuels [52
The uses of biomass extracted from Colombian agriculture also reveal the importance of the biomass devoted to animal feed (Figure 5
b and Figure 6
a), especially that from pastureland grazed by cattle. Although the composition of the livestock intake included significant amounts of crop production, residues, and even imports as contributions to the supply of animal feed, pasture dominated the nutrition of herds by far, particularly cattle, the central element in livestock composition (see Section 3.4
). The pasture was nearly the only source of feed until 1970. After this date, its share fell from 99% to 88% in 2015, since the increase in crop yields raised the space for feeding livestock. Feed imported from abroad started to rise from the beginning of the 21st century, but it only represents 5% of the animal feed extracted from domestic agro-ecosystems.
If we go more deeply into the uses of cropland extraction, the most relevant feature is that primary foodstuffs like cereals, pulses, tubers, or vegetables represent a smaller component than the biomass flows from the cash crops such as fibers, sugar cane, or oil-palm fruit (Figure 6
a and Figure 7
). Only after the food crisis at the end of the 1920s did the amount of primary food for human consumption exceed the amounts of biomass produced in cash crops. At that time, biomass flows of both primary foodstuffs and for market purposes were 3% to 4% of the whole DE. In 2015, the biomass flows extracted from cash crops shared 13% of the total DE, while primary food remained at around 6%.
The primary staple food rose in absolute terms from 0.3 to 2.3 Mt until 1950–1960, when it achieved a share of 4% of DE. Subsequently, this share remained almost flat, at 4–5% up to 2010, when it experienced a slight increase. The biomass devoted to the processing industries through the markets ran almost parallel to that used for primary food until 1970. Yet, with a slightly lower index, until 2015, its share rose from 5% to 13% at a higher rate than staple food (Figure 6
3.4. Livestock and Cropland Intensification
The two main long-term features in the fund-flow metabolic pattern of Colombian agriculture have been the dominance of animal feeding extracted from grassland, especially for cattle, and the dynamism of the cash crops through the industrial intensification of farming. Measured in live units (LU) of 500 kg, the national livestock herd rose two and a half times from 5 to 17.5 LU500 between 1915–2015 (Figure 8
). This increase is due practically entirely to the growth in cattle numbers, which accounted for more than 80% of total livestock fresh weight throughout the period. This increase from 4 to 14 LU500 shaped the general trend, except during the first decade of the 21st century, when it experienced a slight reduction. The reasons for this reduction in the national herd are related to the increasing prices of meat since 1991 that led to a fast de-accumulation of cattle stock to get fresh money, in accordance with the speculative management of the livestock [7
] as well as the increase of violence that rose from the kidnapping of breeders and from cattle thefts [112
]. The number of kidnappings in Colombia increased from 442 to 3456 from 1995 to 2000 and remained at 1356 kidnappings a year on average from 2004–2010 [113
]. Lastly, the main long-term changes in livestock composition have occurred with the fall in the number of mules and donkeys and the increase in pigs and poultry in both absolute and relative terms.
Regarding crop intensification, the indices of domestic crop extraction and area harvested show a close relationship from 1915 to 1945/55 (Figure 9
a), which means that land productivity remained relatively stable. During this period, the increase in production was very land (and labor) dependent. However, after 1955, and especially from 1970 onwards, production growth decoupled from the land. Since then, increases in yield have driven the DE trend for crops since the 1990s when the area harvested fell (Figure 9
a). The average yield of the total biomass extracted per unit of cropland more than doubled between 1915 and 2015 and rose from 1.4 to 5.5 tons of dry matter per hectare. Although there had been some increases in these average yields during the 1930s, the actual change in the trend in yields took place from about 1950 onwards and accelerated until 2000, after which the average yield stagnated (Figure 9
Yield trends differed between staple crops and cash crops. The yields of cereals not only remained under average, but they also grew less than cash crops such as sugar and sweeteners and oilseeds. Yields of sugar crops have risen since the 1930s, moving from 3 to 26 tons of dry matter per hectare between 1930 and 2015. The oilseed yield increased after 1950, moving from 0.6 to 11.6 tons of dry matter per hectare between 1950 and 2015. However, the increase in cereal yields was suddenly interrupted between 1975 (2 tons of dry matter per hectare) and 1995 (2.2) and again from 2003 to 2013 (2.8). Sugarcane became by far the most intensive crop. Nevertheless, this yield had already been attained in 1979 and has remained at that ceiling ever since.
The article presents new data on NPP, extraction, and use of biomass from crops, pastures, and forest between 1915 and 2015 in Colombia. It provides a bio-physical reading of agrarian change as well as identifies the timing and features of the unsustainability of farming carried out in Colombia during the period. From a centennial perspective, the results reveal salient structural continuities, as well as significant changes over time.
The main continuity is the enormous proportion of land and biomass flows taken up by cattle-ranching on pastureland. The grassland production and the pasture as an animal feeding were the main pieces of the biomass extracted and used in Colombia during the twentieth century. Pasture and shrub land are 40% of the land area of the country, but its increase took place after 1970, which affected the forest land especially the Andean forest, and the total NPP. The change in the land cover composition entailed a reduction of 10% of the total NPP during the twentieth century. After 1990, the NPP reduced its rate of change, but its volatility increased. The gains in yields from crops and pastures, and perhaps in the seeded forest management or the rise of coca crops, which are behind the reduction of the NPP fall, are also behind the increase of this volatility.
The land-cattle nexus as a form of land-grabbing affecting land cover and biomass extraction composition, and the behavior of the volatility in the NPP, deserves more research. This quite unusual socio-metabolic feature has nothing to do with the prevailing dietary patterns of the Colombian population. Instead, it comes from a durable mechanism of land reclamation and appropriation used by Colombian elites to prevent the poor rural population of the country having access to the open colonization frontier. The land cover changes to pasture and shrub land and the amount of biomass extracted to feed cattle reflects this capacity of the elites to grab the land of the agrarian frontier colonization and the impact of its strategy on deforestation and NPP over the whole century.
Regarding the historical changes, the dynamics of crop production and the increasing relevance of cash crops are the most relevant issues. The process of intensification and commercial specialization shifted the dominant land use patterns of Colombian cash crops from tobacco and coffee to bananas, sugarcane, palm oil, biofuels, and illegal coca, and contributed to reducing the area under staple crops. This trade-off between staple and cash crops was also affected by the economic policy of each moment. The frontier expansion in Colombia began with the coffee expansion and the insertion of Colombia into the last weave of the First Globalization, but the organic profile of the agrarian system led the country to face a tension between the allocation of resources (land and labor) to staple food and cash crop production. The state intervention during the export-led growth and especially during the stated led growth, help handle the challenge of producing biomass for the international markets and the domestic economy in expansion during the “golden age” (1967–1974).
At the middle of the century, the Green Revolution innovations were actively encouraged by the state. The support to the agrarian frontier expansion first, and the agrarian “modernization” later, are reflected in the expansion of the area harvested during the first half of the century and the increases in the yields from 1955 to 1975. The main gains in decoupling production from land were achieved during this period, but it was a different process for staple and cash crops. Meanwhile, the area under staple crops stagnated, and its yield increases were less intensive and continuous. The cash crops achieved earlier, and higher yields and its harvested area continued to grow. Lastly, after the 1980s, new cash crops to be allocated in the international markets like palm oil or tropical fruits expanded. The area under staple and even the per capita production of grain fell, which threatened the food sovereignty of the country. The economic openness brought the chance to import food and went deeper into cash crop specialization, together with socio-ecological impacts like water grabbing and pollution, soil erosion, and biodiversity losses.
In the case of the changes in crop production and the area harvested, the role of the elites deserves more attention. Medium-sized and small-sized farmers started the frontier expansion that took place during the higher growth rate of coffee and it was supported by the economic policy of the state. The state intervention stabilized and, during the inward economic growth period the agrarian sector was modernized. However, during this period (1950–1975), interest in the cash crops advanced and, at the beginning of the 1970s, the elite slowed the hopes of land access to the small farmers and took the credit to boost their agri-business. This specialization went deeper after 1990, when the economic openness was embraced formally, at the expense of food sovereignty. The rise in cash crops relevance might also mean the start of a new trend of turning the land grabbed through pastures into more profitable export crops, which put in motion a new inner frontier of land-use intensification.
The almost continuous support of the rural elites by the Colombia state and the persistence of the land–cattle nexus as a form of land-grabbing on the open frontiers has reinforced an unequal agrarian class structure. In this context, the socio-ecological impacts of deforestation in Colombia have been the flip side of this coin. They are currently spreading towards the lowland rainforests and the Amazon. The fate of nature conservation and fair human development is, therefore, closely linked with achieving peace and land reform.