The Effects of Population Growth on Land

8/6/2019 The Effects of Population Growth on Land

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The Effects of Population

Growth on Land UseIn an article in Yale Universitys Environment 360, Jonathan Foley,

Director of theInstitute of the Environment, University of Minnesota,

argues that the global community now faces a crisis in land use and

agriculture that could undermine the health, security, and

sustainability of our civilization. While climate change has received

enormous attention (rightfully, Foley argues), human population

growth, and the corresponding rising global demand for meat anddairy products, as well as the growing need for bioenergy from corn,

sugarcane, and other sources should be equal cause for concern.

We are putting tremendous pressure on the worlds resources.

With 70 million new people per year, Foley argues, if we want any

hope of keeping up with these demands, well need to double,

perhaps triple, the agricultural production of the planet in the next

30 to 40 years.

Foley said meeting the agricultural needs of a growing global

population is difficult enough, but, at the same time, countries

must meet growing food production needs while mitigating the

effects of agricultural production on land-based ecosystems.

Already, we have cleared or converted more than 35 percent of the

earths ice-free land surface for agriculture, whether for croplands,

pastures or rangelands. In fact, the area used for agriculture is nearly

60 times larger than the area of all of the worlds cities and suburbs.

Since the last ice age, nothing has been more disruptive to the

planets ecosystems than agriculture.

Agricultural puts pressure on lands, but also on water systems.

Across the globe, we already use a staggering 4,000 cubic

kilometers of water per year, withdrawn from our streams, rivers,
http://e360.yale.edu/content/feature.msp?id=2196http://environment.umn.edu/http://environment.umn.edu/http://e360.yale.edu/content/feature.msp?id=2196


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lakes and aquifers. Of this, 70 percent is used for irrigation, the

single biggest use of water, by far, on the globe. As a result, many

large rivers have greatly reduced flows and some routinely dry up.

And the extraction of water from deep groundwater reserves is

almost universally unsustainable, and has resulted in rapidly

declining water tables in many regions of the world. Future water

demands from increasing population and agricultural consumption

will likely climb between 4,500 and 6,200 cubic kilometers per year,

hugely compounding the impacts of climate change, especially in

arid regions.

Not only are water and land resources put under stress, but current

agricultural practices create pollution. Agriculture, particularly theuse of industrial fertilizers and other chemicals, has fundamentally

upset the chemistry of the entire planet. Already, the use of

fertilizers has more than doubled the flows of nitrogen and

phosphorus compounds in the environment, resulting in widespread

water pollution and the massive degradation of lakes and rivers.

Excess nutrient pollution is now so widespread, it is even

contributing to the disruption of coastal oceans and fishing grounds

by creating hypoxic dead zones, including one in the Gulf ofMexico. Another form of pollution results from current agricultural

and land use practices: C02 emissions. According to Foley, current

practices, including clearing forests for agricultural land, contribute

30 percent of the currently unsustainable C02 emission levels.

Foley points to a few possible solutions: invest in revolutionary

agricultural practices, a new greener agricultural revolution; and

improve agricultural production while also mitigating environmental

impacts. Foley says there is room for hope. In recent years, for

example, U.S. farmers working with agricultural experts have

dramatically improved practices in the corn and soybean belt, cutting

down on erosion, nutrient loss, and groundwater pollution, even as

yields have continued to increase.


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What Is Meant by LandUse Change?

Because of the vertical and horizontal heterogeneity of landscapes,researchers from many disciplines use land survey data. Zoologically

oriented landscape ecologists study the effects of horizontalheterogeneity on animal populations (Merriam, 1984; Forman,1982). Similarly, the data can be used to help answer a key questionfor humankind: Is the survival of groups of people essentiallydependent on landscape heterogeneity? Agriculture and other humanactivities imply it is.

Landscape ecology is concerned with the study of land or landscape,its form, function, and genesis (change). It looks at the factors

interacting at the earth's surface, including the physical, biological,and noospherical actions originated by humans. These factors formthree-dimensional phenomena that can be seen as horizontalpatterns of related elements (units of land) and as vertical patternsof land attributes, such as climate, rock, soil, water, and vegetation.The heterogeneity of these patterns is the main focus of landscapeecology.

A landscape is viewed as a holistic entity that is composed of avariety of relationships in a relatively steady state. The maintenance

of a steady state is called homeostasis, which refers to the set ofpositive and negative feedback factors that keep the system in adynamic equilibrium. The steady state may evolve into anothersteady state over time, but it is protected from strong fluctuations byfeedback factors (homeorhesis).


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Population Pressure, Land

Tenure, and Natural Resource

Management

Massive degradation of natural resources, including forests,rangeland, and irrigation water, has been taking place in the

Third World. Its growing population has increased demandfor land, trees, and water, which, coupled with tenureinsecurity or the absence of clear property rights, hasresulted in the over-exploitation of these natural resources(e.g., Deacon 1994). This in turn has threatened thesustainable development of agriculture, forestry, andlivestock sectors. The critical question is whether the currenttrend will continue and result in further degradation ofnatural resources and, ultimately, the significantdeterioration of human welfare.

Boserup (1965) argued that population pressure need notresult in such disastrous consequences. Rather, she arguedthat it leads to the evolution of farming systems fromlandusing or natural resource-using systems, such asshifting cultivation, to land-saving and laborintensivefarming systems, such as annual cropping.1 Her argument,however, is incomplete: while she acknowledged that

investment is required to establish intensive farmingsystems (e.g., investment in the construction of irrigationfacilities, terracing, and tree planting), she paid insufficientattention to incentive systems which ensure that theappropriate nvestments are made. It is widely recognizedthat investment incentives are governed by the land tenure


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or property rights institution, as it affects the expectedreturns to investments accrued to those who actuallyundertake them (Besley 1995). In sparsely populated areasof Sub-Saharan Africa and islands in the South Pacific, land

is often owned and controlled by the community whereindividual land rights are severely restricted and benefitsare shared widely among members of extended families(Johnson 1972). If such communal ownership of land prevailsand persists, investment incentives are likely to be weakand thus investments necessary for the intensification offarming systems may not be made (Besley 1995; Johnson1972). Then, the extensive and natural resource-using

farming systems may continue to be practiced, contrary tothe Boserupian hypothesis.

Hayami and Ruttan (1985) argued that not only technologiesbut also institutions change in order to save increasinglyscarce resources. This would imply in our context that landtenure institutions change toward individual ownership, soas to provide appropriate investment incentives to conserve

natural resources. Consistent with the induced innovationthesis, a theory of property rights institution developed byDemsetz (1967) and Alchian and Demsetz (1973) asserted,based on the historical experience of hunting communitiesin Canada, that property rights institutions evolve from openaccess to private ownership when natural resources becomescarce. In many parts of Sub-Saharan Africa, it is known thatthe system of communal property rights on cultivatedagricultural fields has been considerably individualized(Bruce and Migot-Adholla 1993). Yet, no systematic researchhas been made as to the effect of population pressure onland tenure or property rights institutions and the effect ofpossible changes in land tenure institutions on theinvestment in land improvement towards the intensification


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of farming systems and the preservation of naturalresources.

Based on the recently completed project concerning land

tenure and the management of land and trees in Asia andAfrica (Otsuka and Place 2001), this paper attempts toidentify the process by which population pressure leads tothe individualization of land rights and its consequences onthe management of land and trees. Particular focus will beplaced on the development of agroforestry systems growingcommercial trees, such as cocoa, coffee, cinnamon, andrubber, which are becoming important farming systems in

agriculturally marginal areas, where people are particularlypoor and natural forests have degraded rapidly (Otsuka2000).2

The conceptual framework is discussed in the next section,which is followed by the examination of the results of casestudies on the management of trees and cropland. Policyimplications of this study are discussed in the final section.

The views expressed in this paper are the views ofthe authors and do not necessarily reflect the viewsor policies of the Asian Development Bank Institute(ADBI), the Asian Development Bank (ADB), its Boardof Directors, or the governments they represent.ADBI does not guarantee the accuracy of the dataincluded in this paper and accepts no responsibilityfor any consequences of their use. Terminology used

may not necessarily be consistent with ADB officialterms..


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Population, Land Use, and the

Environment

As noted earlier in the course, agriculture employs a high proportion of people in the

Third World. In this section, we will look at population growth and agricultural

development, with a particular emphasis on how population growth results in changes in

land use and in utilization of the natural resource base.

The discussion begins with a brief look at the arguments of Boserup concerning induced

technological change in agriculture, and then focuses on Rosenzweig and Binswanger's

broader analysis of the effects of population growth on production relations in agriculture.

We'll conclude with an examination of two case studies: one from Zaire and the other

from Rwanda.

Population growth and production relations

in agriculture: Boserup and beyond

In considering how population growth influences agricultural development,

we begin by noting two points. First, adding more workers to a fixed

amount of agricultural land will, other things being equal, result in a

diminishing marginal product of labor (law of diminishing marginalreturns). Second, it is unlikely that other things will remain equal (i.e.,

unchanged).

More specifically, in our review of the National Research Council's 1986

report on population growth and economic development in the Third World,

we noted that counter to the various arguments that have been made

suggesting that there will be adverse effects of population growth, Ester

Boserup has stressed the notion that there will be positive effects as well.

Most notable in this regard is her view that population pressure on the land

will stimulate the search for and adoption of new technologies of

production. In essence, then, population growth induces technological

change, resulting in higher productivity of agricultural workers.


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Boserup's Table 3.2 (overhead presented in class) shows various food

supply systems, arrayed in order of the frequency of cropping (i.e., the

intensity of land use). The shift from long-fallow to short-fallow systems

and then to annual cropping and multicropping is typically associated not

only with more intensive land use, but also with increasing populationdensity and technological sophistication in agricultural production.

Rosenzweig et al., in the context of a broad-ranging assessment of

production relations in agriculture, provide a concise summary of Boserup's

arguments regarding the effects of population growth on agriculture,

identifying eight principal consequences:

1. reduced fallow periods;

2. increased investment in land;

3. shift from hand-hoe cultivation to animal traction;

4. adoption of soil fertility maintenance via manuring;

5. reduced average cost of infrastructure;

6. encourages more specialization in production activities;

7. induces a change from general to specific land rights; and

8. reduced per capita availability of common property resources such as

forest, bush, and/or grass fallows and communal pastures.

The first four of these effects represent efforts to increase land productivity

and to offset the increased labor requirements stemming from more

intensive cultivation. The fifth and sixth effects are due to economies ofscale resulting from increased population density. The seventh effect

generates incentives to undertake investments in specific plots of land in

order to intensify production and preserve soil fertility. The eighth effect

raises the possibility of overutilization of common property resources (the

"tragedy of the commons").


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Not only the intensity of agricultural production, but numerous other aspects

of production relations in agriculture are affected by population growth and

increased population density. This is best illustrated by Rosenzweig et al.'s

Table 4.1 (overhead presented in class), which shows how markets for land

and labor, credit markets, and various other aspects of production relationsin agriculture are likely to vary between land-abundant settings and land-

scarce economies.


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Boserup and Bandundu: Case study #1

The Boserup induced-technological-change hypothesis, in which there is a

positive feedback from population growth and increased population density

to agricultural development, provides a basis for some optimism. My paper

on "Population Growth, Changing Agricultural Practices, and

Environmental Degradation in Zaire" presents a distinctly more pessimistic

view.

The paper focuses on the province of Bandundu, immediately to the east ofKinshasa. The population density in this predominantly rural province is

rather low (about 19 per square kilometer), and historically food production

has been via a long-fallow system of slash-and-burn agriculture.

Although there has been outmigration from Bandundu to Kinshasa, and

migration of rural residents to the province's urban areas, the rural

population has continued to grow. As the population has increased, more

and more land has come under cultivation. Often this has been more

marginal land, in terms of its capacity to produce food. This process, calledland extensification, in conjunction with growth in the demand for wood as

fuel, has contributed to deforestation.

Agricultural intensification, in the form of shortening of fallow periods, has

also been evident in Bandundu during the past 15-20 years. This

intensification was encouraged not only by population growth within the

province, but also by improved access to the Kinshasa market dating back to

the late 1970s when a major paved road linking the province to the capitalwas completed.

Thus, while some elements of the Boserup scenario are present in

Bandundu, a number of others are not. Indeed, work by Louise Fresco

documents that there have been additional changes in agricultural practices


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designed to economize on labor (e.g., less care in field preparation) that

have had the impact of hastening soil erosion and loss of soil fertility.

There is potential for serious environmental degradation. The gradual

destruction of forest and its replacement by open savanna reduces soilfertility. Present practices entail what Dasgupta referred to as "mining" of

the soil (cf., his suggestion to use NNP, or Net National Product, which

would differ from GNP by taking into account the effects of changes in the

natural resource base on future consumption possibilities).

Overall, then, the situation in Bandundu appears to correspond to that

described by Lele and Stone in their examination of evidence from six

countries in sub-Saharan Africa: "the environmental damage from the

reduction of bush fallow, the more intensive use of land without

supplementary biological and chemical inputs, and the depletion of forestry

resources complicates the transition from low to more densely populated

areas as originally envisaged in the Boserup hypothesis."

The concern for the longer run, then, is that the increases in food production

that have been realized via intensification will not be sustainable over the

long haul. That is, it may not be possible to maintain agricultural yields.

Technology, in the form of improved inputs (high-yielding seeds, fertilizers,

pesticides) does exist that would allow maintenance of yields and even

further increases in food production. However, the debilitated state of

Zaire's economy and transportation infrastructure means that use of

improved inputs is not economically feasible. The long-term prospects,

then, are not at all appealing.

Demographic pressure in Rwanda: Case study #2


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John May's short paper on "Demographic Pressure and Population Policies in

Rwanda, 1962-1994" highlights the fact that Rwanda's economic problems are

like those faced by other countries in sub-Saharan Africa, yet at the same time

more extreme. In large part this is a consequence of the fact that the population

density of 292 inhabitants per square kilometer means that Rwanda's density ismore than 12 times as high as that for all of sub-Saharan Africa.

Fertility has been very high in Rwanda, reaching a total fertility rate of 8.5 and

higher in the late 1970s and early 1980s (see May's Table 2). There is some

evidence of a decline during the 1990s, but fertility was still above 6 as of

1992. This high fertility, in conjunction with declining mortality, has resulted

in substantial population growth (see his Figure 1).

As shown by May's Table 3, this rapid population growth has beenaccompanied by distinct changes in land use. More land is being devoted to

crop production, while less has been available for pastures and fallow. As with

the Bandundu case study, these changes in land use raise serious questions

about environmental degradation and sustainability of food crop production

(cf., impact on mountain gorillas).

May reviews the various population policies that have been attempted over the

past 40 years, beginning with efforts by Belgium during the colonial period to

encourage emigration to neighboring countries such as Zaire. The closing ofborders after independence in the early 1960s ended this policy.

A second resettlement policy, "paysannats," was attempted in 1963, and

entailed resettling people to areas with land available for cultivation. This was

discontinued after only a short period because demand for participation

exceeded the available land.

Policy aimed directly at slowing demographic growth was initiated only in

1981, when the government launched a national family planning program.Although slow in getting started, this program appears to have contributed

(along with delays in marriages due to lack of land) to the modest declines in

fertility observed by the early 1990s. However, as mentioned earlier,

population growth remained high.


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The Effects of Population Growth on Land

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