This document reviews the impacts of small-scale and large-scale tropical agriculture on frugivorous bird species. Small-scale practices like agroforestry have less negative impacts by retaining some primary forest, but often require more land and thus contribute to more deforestation. Large-scale monoculture like oil palm plantations severely reduce biodiversity by removing all primary forest habitat. While it protects some land as forest reserves, it provides no suitable habitat for specialist species like frugivorous birds. To best conserve biodiversity, a balanced approach is needed that uses diverse agriculture near intact forest buffers to support transition species while also protecting large forest areas.

1. Small-scale vs large-scale tropical agriculture impacts on frugivorous avian species: A
review
As primary forest abundance continues to decline as land use practices continue to expand
with global economic demand (Renwick et.al 2014), understanding land use impacts on
native forest inhabitants has never been so important. With the aid of scientific literature, this
study aims to review the various levels of tropical agriculture and its impacts on primary
forest biodiversity and native species, with particular interest in frugivorous birds.
Tropical agriculture
A number of studies classify small-scale tropical agriculture as small managed areas of
altered forest land (approximately 1-5 hectares) aimed at optimising production of a single or
variety of crops by integrating with primary forest or adapting and utilising secondary forest
(Chandler et.al 2013: Tremblay et.al 2014: Kuppler et.al 2015). Agroforestry utilises primary
forest vegetation i.e canopy trees, to provide shade whilst retaining water (Hernandez et.al
2013) to help drought-proof crops, as found in Gutierrez-Velez et.al 2014. Another example
of small-scale agriculture are home gardens and small swidden (also known as slash and
burn) practices. Scales and Marsden 2008 study illustrates that swidden practices farm over
a number of years (approximately 1-5 years) followed by the burning of all vegetation. The
area is then allowed to be fallow to promote soil fertility for approximately 4-15 years in
preparation for replanting. Though swidden crop production is usually intended for local
markets (Tremblay et.al 2014), home gardens are often located in or around the grounds of
a residential home for the purpose of food production for that household via integration with
primary forest flora, particularly canopy cover (Helbig-Bonitz et.al 2015).
When compared to large-scale monoculture, research into small-scale agroforestry indicates
that these practices accommodates a wide range of native flora such as primary forest trees,
which sustain and support a greater fauna biodiversity than intensive large-scale agriculture
(Perfecto et al. 2003; Philpott et al. 2008). However, as most small-scale agricultural
practices are land sharing, more land must be cultivated to produce yields similar to large-
sparing methods which leads to the production of more secondary forest and degradation of
primary forest (Chandler et al. 2013).
Large-scale monoculture practices (50+ hectares) involves the complete deforestation of
primary forest for the purpose of establishing a plantation of a single crop to produce
maximum yield, over a prolonged period of years; as documented throughout many studies
(Koh & Wilcove 2008: Avhar et.al 2011: Senior et.al 2012: Azhar et.al 2014). The most
commonly researched example of large-scale monoculture is the plantation of regimented
palm oil trees for the production of palm oil kernels (over 16 million hectares globally (Lees
et.al 2015)). Which is a commercially utilised product throughout the globe (Koh & Wilcove
2008). Other examples of large-scale monoculture are the production of rice, Cocoa and
bananas which often utilise practices similar to swiddens only on a much larger scale (Azhar
et.al 2014).
The structure and function of the primary forest, impacted upon by the differing types of
agriculture, changes depending on the practice being utilised. As small-scale agriculture
often manipulates primary forest by preserving key species for the benefit of crop plants,

2. mixed crop species are often planted to optimise profit and yield throughout the year and not
in a single seasonal harvest. This is due to the production scale not being as vast as large-
scale agriculture (Renwick et.al 2014). The landscape created by agroforestry is a mix of
sporadic canopy trees in combination with mid-story shrubs and low ground crops such as
rice and coffee. Shrub growth is often controlled to produce optimal conditions for crop
growth over a period of years (Hernandez et.al 2013). The altered primary forest function
serves not only to create produce, but often biodiversity composition of native fauna
changes; creating a beta diversity of native fauna as more hardy species establishes
themselves amongst the newly available niches (Gilroy et.al 2014). Hernandez et.al 2013
study demonstrated that agroforestry often increases insect diversity thus encouraging
insectivores. Which consequently reduces the requirement for pesticides, promoting
microbial soil diversity and prolonging soil quality and crop yield (Scopel et.al 2012).
Agroforestry cropland subsequently become multifunctional, with production of crops as well
as conserving some migrating native fauna by creating succession habitat from remnants of
primary forest.
As large-scale monoculture removes all primary forest habitat, it creates hectors of uniform
forest with no understory, grass cover or mid-story. This often leads to reduced crop yield in
dry conditions as the lack of groundwater retention from complex root systems, cause
plantations to become less resilient to drought as detailed in Gutierrez-Velez et.al 2014
investigation. Many studies have shown that plantations focus on optimising yield by
regimented growth management with the aid of pesticides and chemical fertilisers (Senior
et.al 2012: Azhar et.al 2014). Consequently the function of monoculture production is solely
to produce maximum profit over a period of years via maximising yield and minimising
produce loss. Though a highly productive and profitable practice, Scopel et.al 2012 study
demonstrates that overtime yield will often reduce due to soil degradation. This practice
serves minimal function in the conservation of any primary forests inhabitant species, flora or
fauna. As decline in species can be seen throughout monoculture plantations with retention
of only the hardiest and most niche diverse species (Azhar et.al 2014: Najera & Simonetti
2010). However this is a land sparing practice which allows for the protection of the primary
forest in the form of reserves and parks, by limiting the area of crop production to a limited,
intensely farmed area (Malhi et.al 2013).
Comparatively, small-scale and large-scale tropical agriculture causes less damage to
primary forest biodiversity than some other forms of land use. Investigations found that
although large-scale monoculture may destroy primary forest, the plantation forest it creates
can retain and protect some of the primary forest biodiversity. Whereas practices such as
commercial logging and mining can remove primary forest for the sole purpose of extracting
resources without replacement of any secondary forest, causing significant and detrimental
degradation to soil and groundwater which in turn prevents and delays primary forest
recovery; devastating primary forest biodiversity (Edwards et.al 2010: Deikumah et.al 2014).
Impacts on native fauna
Agricultural practices can affect primary forest residents both negatively and positively
depending on the type of practice used. However, most scientific investigations have
highlighted that frugivorous avian species, and most specialist feeders, are negatively
impacted upon wherever primary forest is disrupted (Deikumah et.al 2014: Gilroy et.al
2014a: Gilroy et.al 2014b) This is due to a number of reasons and often a combination of

3. factors contribute towards declining numbers of frugivorous avian species. Chandler et.al
(2013) and Hernandez et.al (2013) studies compared shade grown agroforestry coffee
production to secondary forest sun grown coffee and found that the integration of open
canopy coffee farming amongst primary forest canopies, produced higher species richness
of birds in comparison to secondary forest farming. However, Chandler et.al (2013) found
that of the species recorded none were frugivorous, yet 82% of the forest dependent species
did remain within shade grown coffee farming. This gives the suggestion that specialist
feeders such as frugivorous birds, are fewer in number and favour primary forest over
cropland; potentially due to poor food availability. The investigation furthermore supports this
theory as it also identified that in the absence of frugivorous bird species, insectivorous
species increased in number due to rising insect abundance. Hernandez et.al (2013)
investigation also indicated that shade grown coffee plantations reflected the composition of
secondary forest communities with minimal primary forest dependent species being
recorded, which could also explain the lack of frugivorous birds as increased competition
could be reducing their abundance. However, the validity of their investigation can be
questioned as the method used gave no explanation for the high levels of recaptures during
the data collecting process. One explanation could be that the radius of analysis was too
small or too far away from the primary forest parameter to give a clear indication of any
native bird species migrating in and out of the coffee plantations.
Though frugivorous bird species abundance is often dependent on food availability (Garcia
et.al 2014), nesting availability has also been documented as a key factor involved in
determining the presence of most avian species. Sheldon et.al (2009) and Styring et.al
(2010) found that industrial tree plantations such as those used for the purpose of pulp
production, often fluctuated in species richness depending on the age of the plantation.
Young plantations were dominated by insectivorous bird species yet as trees matured more
specialist birds arrived. As tree cavities developed, nesting availability increased and in
seven-year-old plantations small frugivorous bird species began to settle within the
plantation, coinciding seed blooming trees. However the study highlighted that throughout
the investigation no large frugivorous birds were observed. This is potentially due to
increased competition from nesting amongst smaller frugivorous and insectivorous species,
alongside the small size of the young plantations cavities and lack of food availability.
Though the study did indicate as the plantation boundaries began to transition into
secondary forest and epiphyte growth became abundant; larger primary forest species
migration did increase. This finding was mirrored by Helbig-Bonitz et.al 2015 study which
indicated that a complex ecosystem encourages the migration of native fauna from primary
forest to within secondary forest and agricultural farmland. Sheldon et.al (2009), Styring et.al
(2010), Gilroy et.al (2014), Hernandez et.al (2013) and Chandler et.al (2013), all found that
agroforestry practices which incorporate a combination of crop plants whilst retaining tall
canopy trees from primary forest provide the best dwellings for birds and promote both
species richness and diversity. Increased mid-story, grassland and ground cover have also
been identified as having a positive impact on bird species richness as a positive correlation
is often found between insectivorous, granivorous and some frugivorous species (Najera &
Simonetti 2010: Sheldon et.al 2009).
Many studies have however demonstrated that one particular agricultural practice is severely
detrimental not just for frugivorous bird species, but all native fauna within a primary forest.
Palm oil monoculture as indicated in both Azhar et.al (2015) and Najera & Simonetti (2010)

4. studies, lacks the complexity and diversity of plant species found within a natural forest.
Consequently, birds, mammals and insects significantly decline in abundance and in
plantations were understory is completely removed, species richness of birds can be
reduced by up to 41% (Najera & Simonetti 2010). This finding supports the theory that of the
native bird species that migrate into agricultural land, most are insectivorous and not
frugivorous. The Najera & Simonetti 2010 study further supports this in its identification that
the use of pesticides among palm oil plantations significantly reduces bird species richness.
Azhar et.al 2015 study found that regular and intensive harvesting cause structural and food
availability changes which impacted further upon any generalist species dwelling within the
plantations. In addition bird species richness decreased as distance from major roads and oil
palm smallholdings decreased. This was also found to be the case with fruit bats, though
increased understory helped promote their numbers. As frugivorous birds share similar food
sources as fruit bats, their decline in number with increased proximity to developed areas
could also be reflected in frugivorous birds which could indicate the presence of humans is
also a deterrent to some species. This is supported by Azhar et.al 2014 study which found
the uniform, linear structure and vigorous maintenance of oil palm plantations even
negatively impacting upon mammal species, with a decline in number where human activity
was abundant.
These investigations draw attention to the importance of vegetation variation not just to
diversify plant species, but to create complexity in habitat structure from understory to mid-
story and canopy. Furthermore, not just within a plantation or cropland but around the
parameter of these cultivated lands too. Without careful consideration of these key habitat
characteristics, native species of primary forest fauna all experienced significant and
detrimental decline due to dramatic alteration in food and habitat availability. With the
greatest detriment being felt by frugivorous birds and mammals.
The future
In order to conserve primary forest biodiversity it is clear that a balance between habitat
complexity in and around cultivated land is needed (Sheldon et.al 2009) whilst maintaining
moderate yield over a number of years. All the reviewed agroforestry investigations provide
strong support for land-sharing, mixed crop agriculture. As it can sustain healthy beta
populations of native species whilst producing a resilient crop yield of diverse produce
throughout the year. However, agroforestry is severely lacking the amenities required to
sustain specialist feeders, such as frugivorous birds. Reconciliation of this downfall could
come from the implementation of unmanaged, mixed vegetation, boundaries around
cropland. This could provide a buffer zone to aid the transition between primary and altered
forest, which could encourage frugivorous species residency. Though, realistically, as initial
cost of adapting to agroforestry practices is high and cropland is already limited (Chandler
et.al 2013), the application of a “buffer zone” is at an economical loss to landowners. Cost
motivates change and unfortunately due to this, land-sparing practices such as intensive
monoculture are favoured due to their low implementation cost and high profit (Tremblay
et.al 2014). Consequently, in order to encourage conservation in tropical agriculture, it must
be either a profitable alternative or a regulated enforcement by a legal body.

5. References
Azhar, B., Lindenmayer, D., Wood, J., Fischer, J., Manning, A., McElhinny, C., Zakaria, M.
(2011). The conservation value of oil palm plantation estates, smallholdings and logged peat
swamp forest for birds. Forest ecology and management, Vol 262: 2306-2315
Azhar, B., Lindenmayer, D., Wood, J., Fischer, J., Zakaria, M. (2014). Ecological impacts of
oil palm agriculture on forest mammals in plantation estates and smallholdings. Biodiversity
conservation, Vol 23: 1175-1191
Azhar, B., Paun, C., Zakaria, M., Hassan, N., Arif, M. (2014). Effects of monoculture and
polyculture practices in oil palm smallholdings on ropical farmland birds. Basic and applied
ecology, Vol 15: 336-346
Azhar, B., Puan, C., Aziz, N., Sainuddin, M., Adila, N., Samsuddin, S., Asmah, S., Syafiq,
M., Razak, S., Hafizuddin, A., Hawa, A., Jamian, S. (2015). Effects of in situ habitat quality
and landscape characteristics in the oil palm agricultural matrix on tropical understory birds,
fruit bats and butterflies. Biodiversity conservation, Vol 24: 3125-314
Chandler, R., King, R., Raudales, R., Trubey, R., Chandler, C and Chavez, V. (2013). A
small-scale land-sparing approach to conserving biological diversity in tropical agricultural
landscapes. Conservation Biology, Vol 27: 785-795
Deikumah, J., McAlpine, C., Marson, M. (2014). Mining matrix effects on West African
rainforest birds. Biological conservation, Vol 169: 334-343
Edwards, D., Larsen, T., Docherty, T., Ansell, F., Hsu, W., Derhe, M., Hamer, K., Wilcove, D.
(2010). Degraded lands worth protecting: the biological importance of Southeast Asia’s
repeatedly logged forests. Proceedings of the royal society B, Vol 278: 82-90
Garcia, D., Martinez, D., Stouffer, D., Tylianakis, J. (2014). Exotic birds increase
generalization and compensate for native bird decline in plant-frugivore assemblages.
Animal ecology, Vol 83: 1441-1450
Gilroy, J., Medina, C., Haugaasen, T., Edwards, D. (2014). Effects of scale on trait predictors
of species responses to agriculture. Conservation biology, Vol 29: 463-472
Gilroy, J., Edwards, F., Medina, C., Haugaasen, T., Edwards, D. (2014). Surrounding
habitats mediate the trade-off between land-sharing and land-sparing agriculture in the
tropics. Applied ecology, Vol 51: 1337-1346
Gutierrez-Velez, V., Uriarte, M., DeFries, R., Pinedo-Vasquez, M., Fernandes, K., Ceccato,
P., Baethgen, W., Padoch, C. (2014). Land cover change ineracts with drought severity to
change fire regimes in Western Amazonia. Ecological applications, Vol 24: 1323-1340

6. Helbig-Bonitz, M., Ferger, S., Bohning-Gase, K., Tschapka, M., Howell, K., Kalko, E. (2015).
Bats are not birds- different responses to human land-use on a tropical mountain. Biotropica,
Vol 47: 497-508
Hernandez, S., Mattsson, B., Peters, V., Cooper, R., Carroll, C. (2013). Coffee agroforests
remain beneficial for Neotropical bird community conservation across seasons. PLOS One,
Vol 8: 1-9
Koh, L and Wilcove, D. (2008). Is oil palm agriculture really destroying tropical biodiversity?.
Conservation letters, Vol 1: 60-64
Kuppler, Jonas., Fricke, J., Hemp, C., Steffan-Dewnter, I., Peters, M. (2015). Conversion of
savannah habitats to small-scale agriculture affects grasshopper communities at Mt.
Kilimanjaro, Tanzania. Insect conservation, Vol 19: 509-518
Lees, A., Moura, N., Silva, A., Vieira, I. (2015). Poor prospects for avian biodiversity in
amazonian oil palm. PLOS one, Vol 10 : 1-17
Malhi, Y., Adu-Bredu, S., Asare, R., Lewis, S., Mayaux, P. (2013). African rainforest: past,
present and futre. Philosophical transactions, Vol 368: 2-10
Najera, A and Simonetti, J. (2010) Can oil palm plantations become bird friendly?. Agroforest
systems, Vol 80: 203-209.
Perfecto, I., Mas, A., Dietsch, T., and Vandermeer, J. (2003). Conservation of biodiversity in
coffee agroecosystems: a tri-taxa comparison in southern Mexico. Biodiversity and
Conservation, Vol 12:1239-1252
Renwick, A., Vickery, J., Potts, S., Bolwig, S., Nalwanga, D., Pomeroy, D., Mushabe, D.,
Atkinson, P. (2014). Achieving production and conservation simultaneously in tropical
agricultural landscapes. Agriculture, ecosystems and environment, Vol 192: 130-134
Scales, B and Marsden, S. (2008). Biodiversity in small-scale tropical agroforests: a review
of species richness and abundance shifts and the factors influencing them. Environmental
conservation, Vol 35: 160-172
Scopel, E., Triomphe, B., Affholder, F., Antonio, F., Corbeels, M., Humberto, J., Lahmar, R.,
Recous, S., Bernoux, M., Blancart, E., Carvalho, I., Tourdonnet, S. (2012). Conservation
agriculture cropping systems in temperate and tropical conditions, performances and
impacs. A review. Agron sustainability and development, Vol 33: 113-130
Senior, M., Hamer, K., Bottrell, S., Edwards, D., Fayle, T., Lucey, J., Mayhew, P., Newton,
R., Peh, K., Sheldon, F., Stewart, C., Styring, A., Thom, M., Woodcock, P., Hill, J. (2012).
Trait-dependent declines of species following conversion of rain forest to oil palm
plantations. Biodiversity conservation, Vol 22: 253-268
Sheldon, F., Styring, A., Hosner, P. (2009). Bird species richness in a Bornean exotic tree
plantation: A long-term perspective. Biological conservation, Vol 143: 399-407
Styring, A., Ragai, R., Unggang, J., Stuebing, R., Hosner, P., Sheldon, F. (2010). Bird
community assembly in Bornean industrial tree plantations: Effects of forest age and
structure. Forest ecology and management, Vol 261: 531-544

7. Tremblay, S., Lucotte, M., Reveret, J., Davidson, R., Mertens, F., Passos, C., Romana, C.
(2014). Agroforestry systems as a profitable alternative to slash and burn practices in small-
scale agriculture of the Brazilian Amazon. Agroforest systems, Vol 89: 193-204