1. Introduction
The sustainability of land-use systems (the combination, at the plot level, of livelihoods that can involve a combination of agriculture, cattle ranching, extractive resources and off-farm labor) in the Amazon and its importance to mitigate the impacts of climate change and biodiversity loss involves the combination of strategies that farm households use to achieve consumption and market-oriented production needs, and forest and biodiversity conservation. Achieving this sustainability involves reconciling demands for the conservation of natural resources and mitigation of carbon emissions, and the need to improve wellbeing and reduce poverty of rural populations.
A previous study in the literature proposes the demo-livelihoods theoretical framework as a novel contribution to integrate theories that aim to understand how the co-evolution of demographic characteristics of farm households with land-use systems and livelihoods at the plot and farm household level [
1]. Farm households in colonist frontiers are, in this case, units of production and social reproduction. This relationship between household demographic dynamics and land use is also affected by opportunities and constrains in the macro-contextual levels, such as environmental policies, infrastructure development such as the opening of roads [
2] and national policies for poverty alleviation.
The objective of this article was to provide novel empirical evidences to test the adherence of the demo-livelihoods theoretical framework [
1] with a retrospective case study of 28 years for the municipality of Machadinho, Brazilian Amazon. In this sense, and hypothesizing that land uses are not independent from demographic dynamic, it analyzed the association between demographic composition and the sustainability of land use production over time—specifically, cattle ranching and cultivation of annuals and perennials, land consolidation through plot acquisition and the use (or conservation) of forestland.
The article is organized in three parts. First, it summarizes key aspects of the Demo-livelihoods theoretical framework [
1] to discuss how and why land-use decisions and the combination of other livelihoods strategies respond to changes in demographic composition, and when they take place at different stages of frontier settlement. Then, it tests the demo-livelihoods hypotheses using retrospective data on the evolution of the colonist frontier of Machadinho, in the southwestern Brazilian Amazon. This study area has been historically characterized by large deforestation (it is within the so-called “arch of deforestation” in the Brazilian Amazon) due to a combination of small- and large-scale agriculture and cattle ranching and infrastructure development projects. Furthermore, four surveys since 1987 collected data on plots and farm households that allow a long-term assessment of changes in livelihoods and demographic dynamics.
The subsequent parts bring a combination of exploratory (descriptive, cluster and correlation) and multivariate hazard analysis to unveil the linkages between land use strategies and household demographic composition changes over stages of frontier settlement in Machadinho.
2. Theories on Demographics Dynamics and Livelihoods over Stages of Frontier Settlement
Several theories have explained the adaptative capacity of farm households to the specific conditions of frontier environments, including the role of household size and composition as causes and/or consequences of these changes. For instance, the
Household Land Use and Life Cycle approach, drawing upon Chayanov’s peasant cycle [
3,
4] and adapted by several authors to the Amazonian context [
3,
5,
6,
7,
8,
9,
10,
11,
12,
13] states that land use and farm labor allocation decisions are contingent on household size and composition at specific stages of frontier development and household life cycles. According to Barbieri [
1]:
“
households adopt specific land uses in periods of low labor availability [initial frontier stages], such as clearing small forests and raising annual crops (at earlier stages when couples have young children). As households accumulate capital over time and have a higher availability of labor (young children becoming teenage children or young adults), they adopt or diversify land use from annual crops to cash crops, perennials and pasture, and increase deforestation (…) [while] Old Dependency Ratio and smaller household size in the post-frontier may indicate an “empty nest effect” [14] with sons or daughters reaching adulthood and leaving to constitute his or her own household, or in search of education or labor opportunities elsewhere.”
Thus, it is assumed that demographic dynamics co-evolves with land use strategies at earlier and intermediate frontier stages, but evolve separately when connections to markets become another component of livelihoods at later stages of frontier development [
1,
11].
Recent studies have reviewed the linkages between demographics and livelihoods framework to discuss strategies beyond land use and off-farm employment in the Household Land Use and Life Cycle approach [
1,
15]. The
Household Livelihoods and Capabilities approach considers “rural livelihoods” as the capacity, assets (or capitals) and activities (and portfolios combining them) of farm households to guarantee livings and subsistence [
1,
13,
16,
17,
18,
19,
20], as well as to diversify livelihoods and risks to subsistence. The way farm households decide for a combination of five types of capitals in order to meet expected livelihoods: natural capital (e.g., forests, water, soil, ecosystem services), social capital (e.g., social and migration networks, access to institutions, family/household and other interpersonal network or arrangements, human capital (e.g., education, qualification, knowledge about local environmental and ecological conditions, health status), physical capital (e.g., means of production owned by the household such as land, tractors and other equipment, communal assets and access to infrastructure development such as road and electricity) and financial capital (e.g., cash income from farm production or from off-farm labor, remittances, government cash transfers) [
13]. The access and profitability of such combination (or portfolio of capitals) is dynamic over time and reflects distinct temporal and spatial specificities at each stage of frontier development [
1,
14].
The third theoretical framework relating household demographics and livelihoods strategies is the
Extended Multiphasic Responses approach. It was built upon Davis [
21] discussion about demographic (fertility regulation and migration) responses to perceived changes in status and welfare given population pressures on limited resources. Bilsborrow [
22,
23] extends Davis multiphasic responses (originally representing urban, industrialized societies) to rural contexts in developing countries, classifying responses as a combination of demographic (fertility control) [
23,
24,
25], economic-demographic (mobility) or economic. This last represents strategies involving land extensification (incorporation of new cultivated land) or intensification (technological improvements in the land). As in Davis [
21], the adoption of responses is concurrent (meaning that when a household choose one response and it delivers the desired outcome, it is less likely the adoption of another response) or “multiphasical” (farm households can also choose simultaneously two or more responses).
Previous studies on the Household Land Use and Life Cycle, Household Livelihoods and Capabilities and Extended Multiphasic Responses approaches have shown that land use and other sources of livelihoods may be connected to household demographic dynamics, including, for example, the effects of household lifecycles on land-use decisions during initial and intermediate stages of frontier development [
11] and the consolidation and diversification of land use systems over stages of frontier development [
19]. While previous studies have focused on specific demographic aspects discussed in the three theoretical frameworks, the Demo-livelihoods Theoretical Framework assess their combined and synergic effects on livelihoods [
1]. This article adds to the extant literature by empirically testing the demo-livelihoods framework, departing from the assumption that farm household production (e.g., land uses and other subsistence and/or market-oriented livelihoods) respond to, and foster further changes, in the demographic composition of farm households. For instance, the Household Land Use and Life Cycle and the Household Livelihoods and Capabilities approaches associate household exposition (time living in frontier environments) with changes in land use strategies (annuals, perennials, pasture, keeping forestland or cattle ranching). While the Household Land Use and Life Cycle approach expand the concept of household exposition to include household size and composition in terms of ageing of household members (a demographic-composition effect of household exposition), farm household labor composition (on and off-farm) and age structure (e.g., dependency ratios), the Household Livelihoods and Capabilities approach expand the portfolio of potential livelihoods to sources of capital not directly related to land uses.
The Extended Multiphasic Responses approach does not explicitly incorporate a temporal dimension (neither by exposition nor ageing) impacting household responses to threats in livelihoods [
26]. However, its integration with Household Land Use and Life Cycle and Household Livelihoods and Capabilities approaches into the demo-livelihoods theory considers fertility and migration (a combination that ultimately, over time, determines household size and composition), together with economic (land use) responses, as adaptation strategies to perceived negative changes in living standards.
The demo-livelihoods theoretical framework implicitly assumes that demographics and livelihoods may be heterogeneous according to specific stages of frontier development. The household portfolio of capitals and livelihoods strategies respond both to the household demographics as well as spatial-temporal contingencies: spatially, given the location-specific characteristics such as infrastructure, connection to regional and national markets and environmental characteristics; and temporally, regarding time of exposure in the frontier and historical, political and cultural factors at each stage of frontier settlement.
Several authors have suggested evolutionary perspectives about the opening and consolidation of frontier areas, especially in the Amazon [
1,
6,
7,
8,
9,
11,
12,
14,
19]. While these perspectives vary in terms of pace, levels and characteristics of development, there is a reasonable consensus in terms of (i) progression from subsistence or semi-subsistence land uses to intermediate and then diversified land-use systems with some degree of market integration [
1,
6,
11,
12,
19,
27,
28]; (ii) frontier evolution being conditioned by macroeconomic and contextual processes articulated to capitalist accumulation strategies [
29,
30,
31,
32,
33]; (iii) frontier evolution, including demographics, livelihoods, the trajectories of settlers and how Amazon frontiers have different ways to connect among them and with local, regional and national markets [
14,
34,
35]; and that (iv) at later frontier stages the influence of household demographic dynamics on land use change decrease due to frontier integration to urban and regional markets [
1,
11,
12,
19,
36,
37].
In a demo-livelihoods perspective, the definition of frontier evolution involves understanding how a given cohort of colonists may experience over time distinct period effects (spatial-temporal contingencies) that are materialized in specific (pioneer, mature, post) frontiers with certain household and livelihoods compositions. As discussed in Barbieri [
1], a pioneer frontier is characterized by initial settlement years (Years representing each stage of frontier development are for illustration purposes since stages may follow, as previously discussed, temporal and spatial contingencies) with relatively low conversion of primary forest to meet basic subsistence needs (mostly using annual crops), younger age composition (and high youth dependency ratio) with cohorts of pioneer migrant colonists living in predominantly nuclear families. Pioneer colonists are also likely to be involved in rural labor circulation and, given the absence of structured labor markets, in informal (including cooperative) labor arrangements. The mature frontier may involve around 7 to 14 years of settlement, when Dependency Ratio decreases since those children in the pioneer frontier age and enter in the farm household labor pool, thus creating advantages to invest in land uses offering higher profitability (pastureland for cattle and perennials). A consequence of these land use strategies is the rapid conversion of primary forest. On the other hand, ageing of pioneer colonists in the post-frontier (15 years or more) increases (particularly old) dependency ratios. This composition change, together with out-migration of sons and daughters (empty nest effect), reduces household labor supply. Farm households are more likely to combine different sources of capital to diversify livelihoods (both on-farm and off-farm).
These conditions in each frontier stage determine specific hypotheses, depicted in
Table 1, on the association between household demographics and livelihoods strategies defining the household portfolio of capitals. It lists a non-exhaustive list of livelihoods/capitals as example. The hypotheses follow three assumptions [
1]. First, while demographic composition in the frontier may change due to the settlement of new cohorts of in-migrants, we assume that changes over time are mostly due to pioneer descendants that stay and eventually assume plot ownership (family plot succession). Second, capitals are not mutually independent in the composition of the household portfolio; rather, they may be conditional or synergic (e.g., social networks, a source of social capital, may be a condition to access urban labor markets and, thus, remittances and wage labor). The release of farm labor for urban employment and/or emigration and out-migration may also be facilitated by multigenerational household arrangements (different generations of families living in the same household). Third, accumulation and accessibility to some capitals depends of household exposition and investments over the medium and long run—particularly regarding sources of human (e.g., education and labor qualification), physical (e.g., land consolidation, cattle) and financial (e.g., income from annual crops and perennials and off-farm employment) capitals, while other capitals may inversely be depleted over time, such as sources of natural capital that depends on keeping forestland in the plot. Other sources, especially social capital, may oscillate over frontier stages due to different accessibility to migration/social networks, markets (e.g., credit, urban labor), governmental institutions and social programs, among others.
4. Results
4.1. Descriptive Analysis
In a first step in the verification of the demo-livelihoods hypotheses,
Table 2 shows descriptive results for variables representing household composition and life cycles and livelihoods, at each stage of frontier development (pioneer, mature, post-frontier). Annuals, perennials and land in pasture are classified as financial capital since they generate income flows from cash crops, cattle ranching or subsistence price-equivalent crops. Primary forest is classified as natural capital since they represent potential income from plot-based natural resources.
As suggested by the demo-livelihoods theory, the mean age of the head and time in the frontier increased over time (resulting from the accumulation of years since arrival in Machadinho), while age dependency ratios decreased from pioneer to the mature stage. Given ageing of pioneers, we assumed that dependency ratios progressively shift from predominantly young to old ratios over time. Older household age structure combined with the empty nest effect and higher on-farm diversification due to capital accumulation may explain higher reliance on hired (off-farm) labor in 2010 vis à vis 1987. There were no data to compare in 1995 and 2015, but the percentages of households with emigrants and out-migrants in 2010 showed the importance of migration as a livelihood strategy.
Mirroring the demographic transition in Brazil and the empty nest effect, household size declines over time. In the 2010 and 2015 post-frontier, the small increase in Sex Ratios may suggest a “masculinization” due to selective female out-migration, with males more likely to stay in the farm due to land succession (while we do not have information on out-migration in 2015, the proportion of females in off-farm employment in 2015 is a good proxy (and hypothetically a prior step) for out-migrant: 56.2%, against 53.8% for males). This selectivity may indicate that the “empty nest effect” due to mobility implies not only accelerating household aging, but also unbalanced sex ratios.
Regarding human capital, education was consistently low for both head and spouse, albeit education of (female) spouses being higher compared to heads. It can be expected that the education of younger generation increases with the expansion of the public education and welfare system in the frontier. As an example, Bolsa Familia is a conditional federal cash transfer program in which vulnerable families receive a monthly remuneration to keep their children attending school and vaccinated (thus increasing levels of human capital). This helps to explain the higher off-farm (especially urban) labor opportunities that demand more, or other types of, qualification and education. Finally, mobility due to off-farm employment also approximates the hypotheses predicted by the demo-livelihoods theory.
Physical capital increased over time in terms of land consolidation (owning other rural plots) and cattle ownership, showing the importance of land extensification. However, there is an important decline in ownership of cattle in 2015, coherent with the decline in pastureland. While cattle ranching continued to be a profitable strategy, its decline may be associated with smaller household size, ageing and labor shortage. As will be seen below, these household compositional changes may trigger adjustments of livelihoods strategies towards less cattle and pastureland vis à vis other sources of financial capital, including off-farm employment and cash transfers (these last increased 42% between 2010 and 2015, from 44.2% to 62.9%). The high proportion of households owning the plot shows that land tenure is a remarkable characteristic of the Machadinho colonization project. Owning a house in the town showed little variation over time.
Income from on-farm activities predominate in the mature and post-frontiers, when farm households increasingly diversify financial capital toward off-farm employment, remittances from out-migration and cash transfers. In fact, access to loans and credits increased from 18.2% in 1995 to 46.9% in 2010 and 61.2% in 2015. These results, combined with the increasing proportion of hired labor, suggest the advancement of institutions (financial and labor markets and the Welfare State) in the post-frontier. Finally, the depletion of plot-based forest and extractive production over time indicates a smaller reliance on natural capital.
The diversification of household portfolio may be facilitated by multigenerational cohabitation arrangements that favor allocation of farm labor pool in activities outside the farm and, thus, reduce risks from relying only on on-farm production. Furthermore, these arrangements are associated with household income security through retirement pensions (usually for the pioneers), or for families with children in vulnerable socioeconomic conditions (the
Bolsa Familia federal cash transfer program). Multigenerational arrangements also facilitate intra-household transfers among members of different generations. Finally,
Table 2 shows that most pioneers were born in the South or Southeast regions of Brazil [
38], but over time, the second generation that was born in Machadinho—and hypothetically more adapted to the frontier environment—became relatively larger [
19].
Overall, and as suggested by the demo-livelihoods theory, longer time of exposure to the frontier environment may facilitate the accumulation and diversification with certain types of capital, such as physical and financial, and some human capital. This accumulation occurs at the expense of the depletion of natural capital (decreasing proportion of forest and use of extractive resources). Social capital may provide access to distinct sources of livelihoods over time, such as institutions promoting land tenure and land accessibility during the pioneer stage [
38], or cohabitation patterns and migration networks favoring labor allocation in profitable off-farm opportunities in the post-frontier.
4.2. Principal Components and Correlation Analysis
While the preceding section show descriptively the evolution of farm household demographics and livelihoods variables over time, the next step was to identify how each frontier stage is related to specific demographic patterns represented by typologies of household composition and life cycles, according to the hypotheses in
Table 1. Using Principal Components Analysis (PCA), only the first two components (I named them scores) showed eigenvalues greater than 1 and, thus, were retained for rotation.
Table 3 shows the estimates for rotated factors, final communalities and the variance accounted for each pair of scores. The labels in the columns define the substantive meaning for each score.
The pairs of scores for pioneer and mature stages have similar meanings. The first score was named younger demographic score (1), since young household composition (dependency ratio) and household size were positively associated and load in the first component. The second score was loaded by off-farm labor negatively associated with age of the head and time in the frontier; thus, it was named early on-farm specialization score (2). Both scores (1 and 2) defined an early position in the life cycle, as predicted by household life cycle approaches.
Since older dependency ratio and age of the head (rather than household size) positively load in the first score of the post-frontier, it was named older demographic score (3). In 2015, time in Machadinho combined with age of the household head to reinforce the importance of ageing households. In contrast to the predominance of age-composition factors, household size and off-farm labor positively loaded in Score 4. Contrary to previous frontier stages when the negative score for the percentage of household members in off-farm employment was not significantly correlated with household size (Score 2), the positive association suggests that larger household size (hypothetically in multigenerational arrangements) combined with less time in the frontier favors off-farm diversification rather than farm labor retention. It was named off-farm specialization score (4).
The next step (
Table 4) was to analyze correlations between demographic patterns (the typology of household composition and life cycles and livelihoods) at each frontier stage. For comparison and simplification, the analysis kept only the variables in
Table 2 that were available in three frontier stages (1987, 1995 and 2010).
All scores in the pioneer and mature frontiers showed a negative association with human capital variables (education of the head and spouse and off-farm employment). In contrast, off-farm employment was positive for all scores in the post-frontier and, in 2015, education was positively significant for off-farm specialization. Considering that, over time, descendants from pioneers in both scores may achieve higher education levels as discussed in the descriptive results, they have access to an important source of human capital that favors off-farm labor allocation in markets demanding higher qualification.
This diversification strategy may be facilitated by multigenerational household arrangements. The demographic scores (1) in the pioneer and mature frontiers showed similarity in terms of positive association with multigenerational households. Both scores (3 and 4) in the 2010 post-frontier, and score 4 (off-farm specialization) in 2015 were positively significant (contrasting to the negative significance of nuclear households), showing the importance of multigenerational households as a source of social capital. Households with the head born in the Amazon (more adapted to the environment) were similar in the specialization scores 2 in the pioneer and mature; and 4, in the post-frontier.
Financial capital showed a positive association with the specialization score (2) in the pioneer and mature frontiers, and a gradual transition of direction from the positive association of on-farm specialization land in pasture in the pioneer and mature frontiers (score 2) to no-significant (2010) and negative association with off-farm specialization in 2015. In contrast, annuals and perennials became positively associated with off-farm specialization strategies, while the negative association of annuals and perennials with older demographic structure and positive significant association with pastureland (as well as cattle, physical capital) in 2015 seemed coherent with the adaptation of ageing household composition to less labor demanding land uses. Thus, household ageing acts to differentiate land use specialization scores within the post-frontier and across frontier stages.
The results showed a significant accumulation of on-farm physical capital from pioneer to mature frontier, strengthening on-farm specialization (score 2). Ownership of other plots was not significantly associated with older demographic composition in 2010, but its negative significance in 2015 suggests that older household structures are less associated with land diversification through plot acquisition or consolidation. On the other hand, demographic scores (1 and 3) showed high correlation from pioneer to mature and post-frontiers in terms of plot ownership and, particularly from mature to 2010 post-frontiers, of ownership of land and/or house in the town (which favors rural–urban mobility). However, as farm households age towards the post-frontier, plot ownership loses significant association with older demographic structure and becomes positively correlated with off-farm specialization.
Natural Capital followed the predicted pattern in
Table 1, but the depletion rate of forests was faster in the pioneer and mature frontiers in the specializations core (2). This indicates a rapid consumption of forests and their replacement by other types of capital, as indicated by higher land in pasture and higher proportion of on-farm income in
Table 2. The results also showed weak or non-association with the demographic score (1) in the pioneer and mature stages and positive association with extractive production in the mature stage. While there was no association with the scores in the post-frontier in 2010, the percentage of forestland in 2015 was positively associated with older demographic score, but negatively associated with off-farm specialization score. This last case suggests that, considering the positive and significant association with land and annuals and off-farm income, land diversification may be achieved at the expense of forestland.
4.3. Multivariate Hazard Analysis of Production Sustainability
Following the hypothesis that the sustainability of land-use production over time is not independent from composition and life cycles,
Table 5 shows the estimates of the multivariate hazard model of production sustainability in 2015. The Old Demographic Score was consistently negative for all categories of plot uses: the higher the association with this score, the lower the hazards of maintaining farm production over time. In contrast, higher association (scores) of farm households with off-farm specialization increases the hazard of keeping the farm production for intermediate levels of physical capital (owning 2 or 3 plots).
The direction of the signal for type of production also differed by plot size. Considering farm households having only one plot, the hazard of keeping production for those having cattle was only 58% of the hazard for those having cultivation. While the association was positive when we considered two or three plots, the hazard ratio practically equal to one suggests that both farm households with cattle or cultivation had a similar risk to maintain the production.
The combination of these results suggests that higher levels of physical capital (especially two and three plots) and off-farm specialization is associated with sustaining farm production for both cattle and perennials. More physical capital (plots) and investment in these land uses allows for diversification strategies that may be synergic (e.g., off-farm income invested in land consolidation and cattle), and thus, more resilience in farm production over time. Thus, if, on one hand (as in
Table 4), farm households with off-farm specialization strategies are less associated with land in pasture (contrary to the older demographic profile), on the other hand, they are more likely to maintain its production over time (
Table 5) and to diversify livelihoods in perennials, off-farm income and sources of human capital (
Table 4). The higher likelihood of farm households with an older demographic profile to terminate production over time seems to be explained by the fact that (
Table 4) the positive association with land in pasture and having cattle is constrained by smaller possibilities to accumulate physical capital (other plots) that create scale and profitability for cattle ranching.
Table 6 unveils the motivations behind land use and livelihoods strategies. The reasons to terminate farm production of the main perennial production (coffee, a highly labor-intensive land use) was associated with household ageing and related factors such as labor drudgeries and health issues. In fact,
Table 4 shows that farm households in the older demographic profile had a negative association with perennials (and, thus, smaller diversification with on-farm sources of financial capital). On the other hand, cattle ranching remains the most important production being kept over time (25% of the plots settled).
Contrary to coffee production in
Table 6, annuals (especially subsistence crops such as rice and corn, but also other annuals) seemed less resilient over time and termination was more related to environmental problems (plagues, land degradation) rather than ageing-related factors. Problems of access to markets—including hiring in local labor markets to replace ageing and/or small farm labor pool—is also important to explain terminating the production of some annuals and perennials. Keeping the production of profitable perennials (especially coffee) continues to be important, particularly for farm households with off-farm diversification strategies (as shown in
Table 4 and
Table 5).
Finally,
Table 5 shows that the stock of primary forest was significantly positive only for farm households owning four or more plots (which seems consistent if we assume smaller pressure on deforestation for smaller ratios of population per hectares). In this case, an additional increase in the proportion of forest increases the hazard of keeping farm production. While diversification with physical capital (owning four or more plots), financial capital (maintaining land uses) and natural capital (primary forest) allows production sustainability over time, farm household demographic composition seems to mediate deforestation levels. In fact, farm households associated with older demographic scores (higher age of the head, longer time in Machadinho and higher old dependency ratio) are more likely to terminate or limit farm production when owning four or more plots and, thus, use less forestland (consistent with the positive association with primary forest in
Table 4).
5. Discussion
Overall, the results show adherence to the hypotheses on the demo-livelihoods theoretical framework (
Table 1). The definition of demographic patterns combining household age composition and life cycle factors are particularly relevant to explain livelihoods strategies at each frontier stage, as predicted by the demo-livelihoods theory. The time of exposition in the frontier allows farm households to accumulate physical and financial as well as some human capital that facilitates access to off-farm employment. Each stage is also related with the accessibility to different sources of social capital that may favor improving and diversifying livelihoods, for example, cohabitation patterns in multigenerational households and migration networks favoring labor allocation in profitable off-farm opportunities in the post-frontier. In the opposite direction, sources of natural capital rapidly decrease over time.
A distinguishing characteristic of frontier settings is that the accumulation of capitals and access to specific sources of capital over time may allow higher resilience through livelihoods diversification and the combination of on-farm and off-farm strategies or, as in the Extended Multiphasic Responses approach, economic and economic-demographic responses [
19]. In fact, the results confirm the hypotheses (
Table 1) that farm households in the post-frontier have more diversified land uses, with perennials and pastureland for cattle ranching as the most important shares of plot land use replacing forestland, and a mix of distinct off-farm sources of financial capital. Such empirical evidences are fundamental to inform public policies targeting the elimination of long-term deprivation and poverty trajectories that undermines land use sustainability in the Amazon.
Diversification strategies are mediated by demographic composition. In fact, the sustainability of farm production is less likely when it combines smaller levels of physical capital (owning only one plot) and older household age composition. However, independent of combinations with physical capital, ageing is a constraining factor in production sustainability, as shown by the negative association between older households and keeping production. This scenario changes when farm household diversify land use systems towards more profitable (and less labor intensive) cattle ranching and some perennials (as shown in
Table 4), more physical capital (land consolidation) and off-farm diversification strategies (as shown by the positive association with off-farm specialization score), replacing, in the household portfolio, losses in the stock of plot-based natural capital. Farm households specializing in off-farm strategies are less associated with cattle ranching (
Table 4) but more likely to keep its production over time as well as to diversify livelihoods in annual/perennials (more labor demanding,
Table 4), physical capital (owning more plots,
Table 4 and
Table 5), and off-farm income and sources of human capital (
Table 4). Furthermore, smaller household labor pool due to the empty nest effect and ageing is not necessarily a constrain for diversification if farm households have scale in (less labor intensive) cattle ranching and producing perennials with more plots, thus releasing farm labor for off-farm diversification strategies.
While keeping production of profitable perennials (especially coffee) continues to be important for farm households with off-farm diversification strategies, households over time are less likely to diversify livelihoods in terms of annual crops. Rather than composition (especially ageing) factors only, this also seems a consequence of smaller environmental sustainability due to plagues and land degradation as well as production costs associated with market accessibility (labor and agricultural inputs constraining land intensification strategies, and selling the production).
As argued by Barbieri et al. [
19], land use and livelihoods diversification should combine environmental and productive sustainability and improve resilience over time in the frontier environment. However, diversification does not necessarily assure improvements in resilience or are a pathway towards sustainable livelihoods. For example, off-farm employment and migration may deteriorate labor conditions in destination areas such as urban labor markets, mining sites (including gold mining
garimpos) and construction sites. These precarious labor conditions reproduce the socioenvironmental unsustainable land uses and livelihoods in the Amazon.
There were two limitations in the results. First, while they indicate an overall adherence to the demo-livelihoods hypotheses, some deviances (such as the faster depletion of capital natural) may be at least partially explained by the periodization of frontier stages. Compared to the 15 years separating mature and post-frontier, the relatively close dates for pioneer and mature frontiers (8 years apart) may have blurred a sharper distinction between them. The distance between data measured for the pioneer frontier (1987) and the initial settlement in Machadinho in 1984 may have lost the period of lower initial deforestation. It is possible that this timing did not fully capture the transition to an experimentation stage [
6] which involves higher adaptation to frontier land use conditions.
Second, while the applicability of the demo-livelihoods theory to other contexts in the Amazon or elsewhere may be supported by the fact that it is built upon the synthesis of long-standing theories and empirical studies, generalizations to other contexts should be taken with caution. The theory does not intend to be universalistic; accessibility to markets, institutions and territories may define distinct household livelihood strategies, depending on their specific time-space context. As multiple frontiers exist according to temporal and spatial contingencies, there are also heterogeneous populations within the same frontier (as shown by the existence of two scores per frontier stages). In this sense, distinct livelihood strategies and trajectories according to different settlement cohorts, socioeconomic and cultural backgrounds may arise at each frontier stage. In order to overcome this limitation, revisiting and adapting the demo-livelihoods theory to context-specific realities is a pathway to aggregate the validity of empirical findings on the co-evolution of demographics and livelihoods predicted by the demo-livelihoods theory.
6. Conclusions
Reconciling sustainable land-use production and livelihoods with conservation efforts (fully land use and livelihoods sustainability) is a complex effort that involves, among other factors, understanding the mediating role of demographic factors. While extant theories have provided only partial explanations, the demo-livelihoods theoretical framework unveils how the co-evolution of household composition and life cycles and livelihoods over distinct stages of frontier development may inform more precise or focused policies aiming to foster sustainability in the Amazon.
In this sense, the article proposed two novel contributions. First, the literature review in
Section 2 showed examples of studies using the farm household life cycles, livelihoods and capabilities or extended multiphasic responses theories to investigate associations between specific demographic factors and sources of livelihoods (mainly land uses) in specific periods of time (that is, these studies are mostly based on cross-sectional surveys). This article used a synthesis of these theories in the demo-livelihoods theoretical framework to evaluate the association between demographic patterns (combining household composition and life cycle factors) and land uses and livelihoods. The justification is that the effects of demographic factors are not independent. For example, selective off-farm employment and emigration (involving younger, adult household labor force), combined with time in the frontier, increase dependency ratios at a specific frontier stage and over time. Thus, the simultaneous combinations of composition and life cycle variables may reveal specific demographic patterns associated with specific livelihoods strategies.
Second, demographic patterns are not static. They may change over time or even show two or more patterns in a population at the same frontier stage, as shown in
Table 3. Identifying and measuring context-specific frontier stages (pioneer, mature and post-frontier) and how they reveal specific associations between demographic patterns and livelihoods was possible with the 28-year dataset for Machadinho. No other empirical study in the Amazon has used such long-term analysis capturing all stages of frontier development.
These contributions revealed how demographic processes and scenarios based on study cases are useful to inform policy pathways to fully land use and livelihoods sustainability in the Amazon. This is not only for the fate of the forest itself and its inhabitants. It also meets global demands to reduce carbon emissions and biodiversity conservation, including those demands coming from the Global North, which has the highest responsibility for the causes and consequences of global warming. In this sense, understanding mechanisms and factors, including demographic, that pressure fully land use and livelihoods sustainability is fundamental to build efficient and focused policy actions. The combination of national policies with international compensation mechanisms should be sensitive to the micro (demographic) factors that create positive synergies and opportunities for effective forest conservation combined with improving livelihoods.
Regarding this last aspect, future research may explore the potential for fully land use and livelihoods sustainability given the momentum with the advancement of demographic transition. Its impact on farm household ageing may, hypothetically, positively impact the preservation of primary forest and forest recovery in traditional colonist frontiers. Considering, as shown by the results, that the conservation of forestland is compatible with maintaining land use production by older farm households owning large stocks of physical capital (four or more plots), and considering ageing as a constraining factor to expand cattle ranching or perennials, using the stock of natural capital in climate change mitigation strategies such as carbon emission markets and bioeconomy may meet demands for diversification and improving sustainable livelihoods compatible with the post-frontier demographic composition and life cycle.
This scenario of ageing frontier households highlights the increasing importance of governmental cash transfers (such as pensions) targeting the elder in the definition of livelihoods. In addition to governmental and institutional changes, future research may explore the role of other macro, contextual changes in the mediation of the linkages between household demographics and livelihoods. While this article focused on the micro (plot and farm household) dynamics in a colonist frontier, it can be articulated with other types of frontiers, such as those associated with the expansion of agribusiness, mining, and large-scale infrastructure development (roads, dams, etc.). As these multiple frontiers may co-exist and compete for resources, they generate conflicts and opportunities that influence the sustainability of colonist livelihoods.
Finally, given the potential impacts of climate change on land use and land cover change in the Amazon [
44,
45], future research may explore the role of demo-livelihoods transitions on the adaptation to these impacts. This is a particularly important issue since future demographic dynamics may be increasingly conditioned by the pace and level of risks and disasters associated with environmental (particularly climate) change.