Establishing priorities for future land conservation to maximise biodiversity conservation and other ecosystem services in the Tilarán Mountains of Costa Rica

Abstract

The Monteverde-Arenal Bioregion (MAB), located in the Tilarán Mountains of north-central Costa Rica, contains some of the most biodiverse habitats in Costa Rica and also provides the backbone for some of Costa Rica’s most important ecotourism destinations. Several national parks and private preserves protect a large area of habitat in the region, but this complex of protected areas is isolated from other large protected areas because of deforestation associated mostly with agricultural development, plus a smaller amount of urban development. Furthermore, we are aware of no detailed analysis to identify landscapes in need of protection in order to secure the conservation of the region’s biodiversity into the future. Using GIS technology, we analysed select conservation-related ecosystem services in order to identify the lands of highest future conservation priority outside of existing protected areas in the MAB. We identified large areas of habitat on the Pacific slope to the south and west of the existing protected areas and habitat adjacent to Lake Arenal to the northwest of existing protected areas as having the highest ecosystem services values. In contrast, most lands on the Caribbean slope outside of the existing protected areas had comparatively lower ecosystem services values. Based on this analysis, we recommend that future conservation efforts, including potential land purchase, should focus on conserving mid-elevation Pacific slope forests and land along previously proposed biological sub-corridors that could connect the MAB to other existing protected areas. Our analysis shows that many important landscapes for biodiversity conservation in and near the MAB currently exist outside of protected areas, making many species found in those areas vulnerable to human activities. The opportunity to connect currently protected areas to one another through effective biological corridors still remains, possibly through conservation partnerships with landowners or direct land purchase, but time could be short as increasing development and changing land-use patterns threaten to further isolate habitats in the MAB.

Full text

243
Establishing priorities for future land conservation to maximise
biodiversity conservation and other ecosystem services in the
Tilarán Mountains of Costa Rica
Lindsay Stallcup1, Matthew D. Moran1, Doris Rojas1, Erich Mata1
1 Monteverde Conservation League, Children's Eternal Rainforest, Monteverde, Puntarenas, Costa Rica
Corresponding author: Matthew D. Moran (moran@hendrix.edu)
Copyright: © Lindsay Stallcup et al.
This is an open access article distributed under
terms of the Creative Commons Attribution
License (Attribution 4.0 International – CC BY 4.0).
Research Article
Abstract
The Monteverde-Arenal Bioregion (MAB), located in the Tilarán Mountains of north-central
Costa Rica, contains some of the most biodiverse habitats in Costa Rica and also provides
the backbone for some of Costa Rica’s most important ecotourism destinations. Several
national parks and private preserves protect a large area of habitat in the region, but this
complex of protected areas is isolated from other large protected areas because of defor-
estation associated mostly with agricultural development, plus a smaller amount of urban
development. Furthermore, we are aware of no detailed analysis to identify landscapes in
need of protection in order to secure the conservation of the region’s biodiversity into the fu-
ture. Using GIS technology, we analysed select conservation-related ecosystem services in
order to identify the lands of highest future conservation priority outside of existing protect-
ed areas in the MAB. We identied large areas of habitat on the Pacic slope to the south and
west of the existing protected areas and habitat adjacent to Lake Arenal to the northwest of
existing protected areas as having the highest ecosystem services values. In contrast, most
lands on the Caribbean slope outside of the existing protected areas had comparatively low-
er ecosystem services values. Based on this analysis, we recommend that future conser-
vation efforts, including potential land purchase, should focus on conserving mid-elevation
Pacic slope forests and land along previously proposed biological sub-corridors that could
connect the MAB to other existing protected areas. Our analysis shows that many import-
ant landscapes for biodiversity conservation in and near the MAB currently exist outside of
protected areas, making many species found in those areas vulnerable to human activities.
The opportunity to connect currently protected areas to one another through effective bio-
logical corridors still remains, possibly through conservation partnerships with landowners
or direct land purchase, but time could be short as increasing development and changing
land-use patterns threaten to further isolate habitats in the MAB.
Key words: Biological corridors, Costa Rica, GIS, land-use, Mesoamerica, Tilarán Moun-
tains, tropical forest
Introduction
The Monteverde-Arenal Bioregion (MAB), located in the Tilarán Mountains of
Costa Rica, has some of the highest biodiversity in Central America and simul-
taneously represents one of the most important ecotourism destinations of the
Academic editor: João Pompeu
Received:
19 November 2024
Accepted:
8 February 2025
Published:
30 April 2025
ZooBank: https://zoobank.
org/1D34FA5C-A9FF-4F48-BEC9-
45729CD80C74
Citation: Stallcup L, Moran MD,
Rojas D, Mata E (2025) Establishing
priorities for future land conservation
to maximise biodiversity conservation
and other ecosystem services in
the Tilarán Mountains of Costa
Rica. Nature Conservation 58:
243–260. https://doi.org/10.3897/
natureconservation.58.142210
Nature Conservation 58: 243–260 (2025)
DOI: 10.3897/natureconservation.58.142210

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Nature Conservation 58: 243–260 (2025), DOI: 10.3897/natureconservation.58.142210
Lindsay Stallcup et al.: Conservation priorities in a tropical forest
country (Aylward et al. 1996; Langholz et al. 2000; Koens et al. 2009; Stuckey
et al. 2014). The area has several important public and private protected areas,
the most important amongst them being the privately owned Children’s Eter-
nal Rainforest (22,600 hectares) and Monteverde Cloud Forest Reserve (4,125
hectares) and the state-owned Arenal Volcano National Park (12,124 hectares),
Alberto Manuel Brenes Biological Reserve (7,800 hectares) and Santa Elena
Cloud Forest Reserve (310 hectares). Along with a number of smaller, most-
ly privately owned protected areas, the total area in conservation in our study
area is about 50,000 hectares, including protected habitat in eight Holdridge life
zones (Holdridge 1947, 1967; ve regular + three transitional zones) on both
Caribbean and Pacic slopes (Fig. 1).
The region is noted for its high biodiversity, especially for plants, amphib-
ians and birds (Haber 2000; Wheelwright 2014; Newcomer et al. 2022). For
example, the Monteverde area (dened as all lands above 700 m a.s.l. in
the MAB) alone contains over 450 species of orchids, perhaps the greatest
diversity in the world for a single area of similar size (Haber 2000). Numer-
ous endemic species exist here (Newcomer et al. 2022), probably because
of the relative isolation of the higher elevation habitats. The region is also
home to a number of endangered or threatened species (e.g. Bare-necked
Umbrellabird (Cephalopterus glabricollis), Baird’s tapir (Tapirus bairdii)), fur-
ther solidifying the MAB as an important priority for conservation efforts in
Costa Rica and beyond.
Figure 1. Study area showing boundaries of analysis (red outline), protected areas with ownership designation and pro-
posed biological sub-corridors (in yellow outline) Moran et al. (2019).

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Nature Conservation 58: 243–260 (2025), DOI: 10.3897/natureconservation.58.142210
Lindsay Stallcup et al.: Conservation priorities in a tropical forest
The area also is a prime location for ecotourism, with Monteverde and La
Fortuna (as well as smaller nearby communities) hosting hundreds of thou-
sands of national and international visitors annually (Koens et al. 2009).
These high visitation rates, in turn, support a vibrant tourism economy fo-
cused on nature and biodiversity (Aylward et al. 1996; Langholz et al. 2000;
Koens et al. 2009; Stuckey et al. 2014). Charismatic avian species such
as the Resplendent Quetzal (Pharomachrus mocinno) and the Three-wat-
tled Bellbird (Procnias tricarunculatus) are major attractions, as are dra-
matic geological features, such as the Arenal Volcano and associated hot
springs. Subsequently, a large proportion of the local human population is
involved in tourism and, in general, there is a strong conservation ethic in
the local communities where ecotourism thrives (Newcomer et al. 2022).
While conservation efforts in the Monteverde-Arenal Bioregion have been
successful, most of the land that has been protected to date is at higher eleva-
tions and/or includes steep terrain and is not well suited for traditional land use,
such as agriculture. Lower elevations in the region remain mostly unprotected,
resulting in an island of conservation in a larger sea of partial deforestation
and development (Sánchez-Azofeifa et al. 2003; Moran et al. 2019). As a result,
the MAB has lost connectivity with surrounding habitats, perhaps limiting the
persistence potential of organisms that require large, connected tracts of hab-
itat (e.g. jaguar, Panthera onca). However, studies have shown that this region
retains much of its biodiversity, including large mammals that require exten-
sive habitat (Zamzow et al. 2018) and that partially forested, privately owned
corridors connecting the Tilarán Mountains to other protected areas do persist
(Moran et al. 2019; Beita et al. 2021). As conservation efforts have primarily
been focused on higher elevations, lower elevation slopes and their associated
life zones (some of which are completely unprotected in our study area) and
unique species remain vulnerable to deforestation and other negative impacts.
The MAB is also part of the Mesoamerican Biological Corridor, one of
the most diverse ecoregions of the world, representing one of the identied
hotspots of biodiversity on Earth. This large corridor connects the distant biore-
gions of the North and South American continents and is, therefore, of out-
standing importance for both animals that need large ranges (e.g. Panthera
onca) and species that migrate seasonally across the region (e.g. migratory
Neotropical birds). Therefore, successful land conservation in this region will
further the goals of larger Mesoamerican biodiversity protection (Miller et al.
2001; Harvey et al. 2008; Holland 2012; Jiménez-López et al. 2023).
In this study, we analysed select ecosystem services for landscapes in
and around the Monteverde-Arenal Bioregion through the use of geographic
information systems (GIS). Our goal was to identify priority lands for future
conservation efforts, including direct purchase as well as other conservation
initiatives. We hoped that we could identify areas that would be best utilised
for conservation, while simultaneously identifying lands that are better left to
remain in traditional economic activities, such as agriculture, businesses and
other human infrastructure. We also sought to identify suitable potential biolog-
ical corridors that could connect the MAB to nearby protected areas, as such
corridors would represent high priority land for conservation for their ability to
reduce regional fragmentation.

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Nature Conservation 58: 243–260 (2025), DOI: 10.3897/natureconservation.58.142210
Lindsay Stallcup et al.: Conservation priorities in a tropical forest
Methods
Study region
We studied the area in and around the MAB, located in the Tilarán mountain range
of north-central Costa Rica, one of most important protected areas in Central
America (Newcomer et al. 2022, Fig. 1). This area is known for its high biodiversi-
ty, variety of Holdridge life zones (Fig. 2A, B), geological features, water resourc-
es and thriving ecotourism economy. The region is somewhat geographically
isolated from other highland areas and, unsurprisingly, endemism rates are high,
particularly for plants and amphibians (Haber 2000; Pounds and Fogden 2000;
Wheelwright 2000). The MAB has a series of noteworthy reserves and parks, cre-
ating a contiguous block of about 50,000 hectares of protected land, as well as
several smaller, discontinuous protected areas along the margins (Fig. 1). Lower
elevation areas surrounding the MAB remain largely unprotected, meaning that
the complex of parks and preserves is essentially an island of forest surrounded
by a sea of fragmented habitat (Fig. 2C). However, some partially- to mostly-for-
ested corridors still exist, presumably allowing for dispersal of some organisms
northwest into protected areas in the Guanacaste mountain range and southeast
Figure 2. Photographs of landscapes within the study area A Peñas Blancas Valley on the Caribbean slope of the MAB
area B San Luis Valley on the Pacic slope of the MAB; much of this area is secondary forest that has regenerated in the
last three decades C fragmented habitats lower on the Pacic slope showing heavy deforestation and fragmentation due
to agricultural activity D partially forested, but largely unprotected corridor (about 2/3rds native forest) between the MAB
(Arenal Volcano National Park visible on far right of photo) and Tenorio National Park protected lands.

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Nature Conservation 58: 243–260 (2025), DOI: 10.3897/natureconservation.58.142210
Lindsay Stallcup et al.: Conservation priorities in a tropical forest
towards protected areas in the Central Highlands (Moran et al. 2019, Fig. 2D).
For instance, after decades of apparent absence, the jaguar (P. onca) has recol-
onised the region’s protected areas in small numbers (Zamzow et al. 2018, MDM
and LS, personal observations), presumably using such dispersion corridors.
We chose to analyse the landscapes adjacent to protected areas within
the MAB, plus areas around the two biological sub-corridors proposed in Mo-
ran et al. (2019). We examined all lands within a 5 km radius of the boundar-
ies of existing protected areas and the two proposed sub-corridors (Fig. 1).
The north-western and south-eastern limits of the study were the two largest
protected areas nearest to the MAB: the complex formed by Tenorio Volca-
no National Park and the Tenorio Volcano Protected Zone (hereafter, “Tenorio
complex”) and Juan Castro Blanco National Park, respectively. The total area
analysed (i.e. study area) was about 174,000 hectares.
Ecosystem services calculations
While there are numerous ecosystem services for all landscapes (TEEB 2010),
we chose six which we suggest are important for the study area and for which
there are adequate data available for Costa Rica and for our study area in partic-
ular (Table 1). For each of these six ecosystem services, we calculated a relative
value for all locations within the study area to indicate each location’s conser-
vation priority with respect to that ecosystem service. Each ecosystem service
(ES) was weighted equally. We recognise that the decision to weigh all six ES
equally is arbitrary and that a great variety of additional models could have been
constructed. Spatial data for constructing the maps were obtained from a variety
of sources: ES #1 directly from authors of a published paper (Moran et al. 2019),
ES #2, 3 and 4 from the National Territorial Information System of Costa Rica
(Sistema Nacional de Información Territorial, SNIT 2023), ES #5 from biodiversity
data from Kohlmann (2011) and applied spatial data from SNIT (2023) and ES#6
from information provided by relevant hydroelectricity producers.
For each ES, we ranked individual locations with a score of 0, 1 or 2, with zero
being the lowest priority and 2 being the highest priority (see individual descrip-
tions, below). We recognise that there is a certain level of arbitrariness to this de-
cision; for the quantitative measures, we generally divided the values into 33.3%
percentiles. While we have considered these ecosystem services separately,
Table 1. List of selected ecosystem services measured in this study with short descriptions of their value to conservation.
Ecosystem Service Benets Method of Calculation
biological corridors migration/dispersal of species, genetic
connectivity, reduced mortality
arbitrary assignment of value (0, 1 or 2)
protection of land with
steep slopes
reduced soil erosion, reduced landslide risk, water
quality
assignment of value based on slope angle
land-use/forest cover carbon sequestration, ecotourism, biodiversity
protection, local climate and air quality
assignment of value based on forest, pasture or
urban development
life zones biodiversity assignment of value based on zone-specic
biodiversity, rarity and level of protection
biodiversity genetic wealth, ecotourism, ecosystem assignment of value based on endemism and
overall species diversity
hydroelectric generation clean electricity, economic well-being assignment of value based on watershed-specic
power generation

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Nature Conservation 58: 243–260 (2025), DOI: 10.3897/natureconservation.58.142210
Lindsay Stallcup et al.: Conservation priorities in a tropical forest
we recognise that some of these ecosystem services interact in complex ways
(e.g. steep slopes have both high erosion potential and high hydroelectric gen-
eration potential). Conserving the ecosystem services which we studied in this
project is also likely to enhance additional services for which we lack data.
Biological corridors and connectivity
We considered the following areas, which would reduce regional habitat frag-
mentation, to be high priority landscapes for conservation: existing biological
corridors as dened by Costa Rica’s National System of Conservation Areas
(Sistema Nacional de Areas de Conservación, SINAC); forested land that would
connect existing protected areas in the MAB to nearby protected areas; and
private inholdings completely surrounded by existing protected areas. We as-
signed high conservation priority to the two sub-corridors proposed in Moran
et al. (2019). These sub-corridors are located within larger biological corri-
dors as dened by SINAC and would connect the complex of preserves in
the MAB to the Tenorio Complex to the northwest and Juan Castro Blanco
National Park to the east. We also included the Bellbird Biological Corridor,
an existing initiative on the Pacic slope with the objective of improving and
conserving ecological connectivity between high elevation cloud forests in the
Tilarán mountain range and the mangrove forests along the Gulf of Nicoya
(Fig. 1). The Bellbird Biological Corridor spans 11 Holdridge life zones, from
1,800 m a.s.l. to sea level and protects habitats that are important for season-
al altitudinal migrants, including the endangered Three-wattled Bellbirds (P. tri-
carunculatus) and many species of butteries. We assigned private inholdings
within the Children’s Eternal Rainforest (at the heart of the MAB) and the two
proposed sub-corridors from Moran et al. (2019), a value of 2, land within the
Bellbird Biological Corridor a value of 1 and all other land a value of 0.
Slope
We used slope as a proxy for the ecosystem service of soil conservation and
erosion prevention. Landslides are also costly to infrastructure and hazards to
human life, so preserving forest cover on steeply-sloped land has numerous
societal benets (Kjekstad and Highland 2009; Lehmann et al. 2019). We de-
ned three ranges of slope angle: < 5%, 6 to 35% and > 35% and assigned them
values of 0, 1 and 2, respectively.
Land-use
We dened three basic categories of land use: forest, pasture and developed/in-
tensive agriculture (i.e. urban, suburban, other human structures and permanent
crops), based on the GIS data available for the study area. Available databases
do not differentiate between native forest (dened as both primary and sec-
ondary forest) and plantation forests; however, the vast majority of forests in
the study area are naturally occurring (Moran et al. 2019; MDM personal obser-
vations). We assigned existing forest the highest potential conservation value
(2) and developed/intensive agricultural areas the lowest value (0), due to the
existing economic value of this land and the low likelihood of its conversion

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Nature Conservation 58: 243–260 (2025), DOI: 10.3897/natureconservation.58.142210
Lindsay Stallcup et al.: Conservation priorities in a tropical forest
to natural habitat. While primary forest tends to support the highest biological
diversity, in this study, we regard primary and secondary forest as equal con-
servation value. In this region of Costa Rica, natural reforestation is rapid and
tends to support high biodiversity within a short period of time (Janzen and
Hallwachs 2020). Pasture lands were assigned a value of 1, since natural refor-
estation to native habitat is both possible and has commonly occurred in the
study area (Chacón-Cascante et al. 2012; Stan and Sanchez-Azofeifa 2019).
Life Zones
We assessed the value of each Holdridge life zone (Holdridge 1947) in our
study area, based on a combination of life zone rarity (i.e. the proportion of the
total study area for each particular life zone) and degree of current protection
(i.e. the proportion of each life zone currently under protection within the study
area). We utilised the following formula:
Life Zone Priority = (Alz / At) * (Ap / Alz)
where: Alz = area (hectares) of life zone in the study area, At = total study
area (hectares) and Ap = area (hectares) of life zone officially protected
within the study area.
This formula produced an inverse relationship: lower scores indicate rare
and poorly-protected life zones that should be given higher conservation priori-
ty, while high scores indicate life zones that are already well-represented within
existing protected areas in the study area and, therefore, are of lower conser-
vation priority. Life zones with a score of 0 (i.e. 0% protected) were assigned
a value of 2; life zones with a score of 0.01 to 0.05 were assigned a value of 1;
and life zones with a score of 0.05 or greater were assigned a value of 0.
Biodiversity
We assigned a numerical value to biodiversity based on two variables, num-
ber of endemic species and species richness, of selected groups for which
there is reliable country-wide data as calculated by Kohlmann (2011). These
groups included two taxonomic groups of insects (Scarabaeinae, Dynasti-
nae), three plant families (Araceae, Arecaceae, Bromeliaceae) and sh (Os-
teichthyes). While these select taxonomic groups are not an exact measure
of biodiversity (and sh are species-poor in the study area), the unfortunate
paucity of specic biodiversity data for many tropical ecosystems and for
our study area in particular, precluded an exact measure of total biodiver-
sity. However, plant diversity is often a suitable proxy for total biodiversity
(Brunbjerg et al. 2018) and the protection of endemic species is a particu-
larly high priority for conservation (Cañadas et al. 2014).
The number of species + the number of endemics was summed and these
values divided into 33.3% percentiles, then assigned values on the 0–2 scale
used in the other ecosystem services measured. One Holdridge Life Zone
lacked biodiversity data (Bosque Pluvial Montano Bajo), so it should be noted
that this life zone had a lower potential total conservation value in the nal cal-
culation as compared to the others.

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Lindsay Stallcup et al.: Conservation priorities in a tropical forest
Hydroelectric generation
Costa Rica has a largely carbon-free electricity grid (Teske et al. 2020) and
the majority of the country’s electricity comes from hydroelectric generation.
We assumed that forested land in watersheds with hydroelectric projects is of
greater value with respect to the ecosystem service of electricity generation
than forested land in watersheds without hydroelectric facilities (Chang 2006).
We divided our study area into sub-watersheds and acquired hydroelectric gen-
eration data (MWh per year) for the six hydroelectric projects located within the
study area. We then divided the total annual generation (MWh) of each hydro-
electric project by the total number of hectares in the catchment upstream of
the hydroelectric project. The end result was a range of 0–17.84 MWh/hectare
for each watershed (some watersheds have more than one hydroelectric proj-
ect). Watersheds with a value of 15.0 or greater were assigned a score of 2; wa-
tersheds with a value of 5.0–14.9 were assigned a score of 1 and watersheds
with a value < 5.0 were assigned a score of 0.
Final formula
The values from the six ES categories were totalled to produce a total priority
score, with a minimum – maximum range from 0 to 12. These values were then
plotted on to a “heat map” of the study area to show land with the highest com-
bined ranking of ecosystem services and that should, therefore, be considered
of highest conservation value for future conservation action.
Results
The MAB has large altitudinal gradients over a relatively small geographi-
cal area, resulting in many steeply-sloped lands (Figs 2A, B, 3). Most of the
existing protected areas occur at higher elevations and in areas of steep
slopes. Outside of the existing protected areas in our study area, the Pacic
slope to the south and west has large areas of steeply-sloped landscapes
(Fig. 2C), while land to the north and east of the existing protected areas is
comparatively at. The proposed sub-corridor connecting the MAB region to
Juan Castro Blanco National Park has smaller areas of steeply-sloped lands,
primarily in the major river valleys.
Land use in the study area is highly correlated with land already under some
measure of conservation or protection. Unsurprisingly, protected areas are al-
most entirely covered in tropical forest (of various life zones), which is the nat-
ural land cover of the entire region (Fig. 4). There are large patches of forest
located to the south and east of the existing protected areas, especially in and
around the proposed sub-corridor connecting the MAB to Juan Castro Blanco
National Park. Smaller forested areas exist on the Pacic slope to the south-
west of existing protected areas and there are other small patches of forest in
the proposed sub-corridor connecting the MAB to Tenorio National Park to the
northeast. Most non-forested land in the study area is pasture land devoted
to cattle ranching (both dairy and beef, MDM personal observations), although
substantial areas to the northeast of the main protected areas have cultivated
crops (these areas also correspond to the lands with more gentle slopes, Fig. 3).

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Lindsay Stallcup et al.: Conservation priorities in a tropical forest
Figure 3. Slope angle within study area.
Figure 4. Land-use within the study area.

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Lindsay Stallcup et al.: Conservation priorities in a tropical forest
The study area spans 11 Holdridge life zones. Most of the protected areas
of the MAB fall within the lower montane rainforest and premontane rainforest
life zones, with smaller areas of tropical wet forest transition to premontane
(Fig. 5). The other eight life zones present in the study area are poorly protected
and three are completely unprotected. Most notably, on the Pacic slope to the
south and west of the existing protected areas, there is a series of closely alti-
tudinally-spaced life zones that fall almost entirely outside of protected areas
and also have high biodiversity values (Fig. 6) and some intact forest (Fig. 2C).
Conversely, many lower elevational Caribbean slope life zones are also unpro-
tected in their entirety within the study area, but are also almost totally cleared
of native vegetation due to agricultural activity (Fig. 4).
There are six major hydroelectric projects within the study area: one on the
Pacic slope and ve on the Caribbean slope (Fig. 7), the area that receives
the most rain (Waylen et al. 1996). The Arenal facility is the most important
generation facility in the study area, producing about 30% of Costa Rica’s total
hydropower. In total, more than 1 million MWh are produced annually from
water provided by protected areas of the MAB, about 10% of Costa Rica’s
total electricity production and about 13% of its hydroelectric power genera-
tion (Our World of Data 2023), even though it represents less than 5% of the
country’s terrestrial area.
When we combine all of the selected ecosystem services, the areas that
should be given highest priority for conservation are generally located in two
distinct locations: land on the Pacic slope to the south and west of the existing
Figure 5. Holdridge life zones within the study area.

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Lindsay Stallcup et al.: Conservation priorities in a tropical forest
Figure 6. Life zone-specic biodiversity rankings within the study area.
Figure 7. Hydroelectric resources within the study area.

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Lindsay Stallcup et al.: Conservation priorities in a tropical forest
protected areas and land connecting Arenal National Park with the Tenorio
Complex to the northwest of Lake Arenal (Fig. 8). Land to the northeast of the
existing protected areas is generally of lower conservation priority. The connec-
tivity gap between the MAB and Juan Castro Blanco National Park is made up
mostly of lower priority lands with fewer ecosystem services as compared to
the gap between existing protected areas and the Tenorio Complex.
Discussion
Our analysis conrms the existence of unprotected lands with high conserva-
tion value in the vicinity of the existing protected areas of the MAB that should
be the target of conservation activities. There are also areas that have compar-
atively less conservation value, showing that these types of analyses can help
to prioritise the limited resources available for conservation. At this point in
time, differentiating land more suitable for traditional economic activity from
land that would be better utilised for protection of natural resources will be
critical as societies try to balance economic needs with environmental and
ecosystem services protection. This balance is even more critical for coun-
tries like Costa Rica, whose strong tourism (and especially ecotourism) sector
outweighs benets from extractive activities and depends on a healthy natural
environment to sustain its economic well-being.
The rst area which we identied as high priority for conservation includes
lower elevations on the Pacic slope to the south and west of the existing pro-
tected areas in the MAB. This region has a high number of closely altitudinal-
Figure 8. Conservation priority lands within the study area, based on all ecosystem services values included in the analysis.

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Lindsay Stallcup et al.: Conservation priorities in a tropical forest
ly-spaced life zones, several of which have high species diversity and ende-
mism. The life zones in this area are also poorly protected in the study area
(and in Costa Rica in general). As the climate in these life zones tends to be
favourable for cattle ranching and coffee growing, much of this habitat was
deforested many years ago for agricultural use. However, some forested areas
remain, especially on steep slopes and in riparian zones. Additionally, these
areas have experienced an increase in reforestation over the past few decades
as the more marginal agricultural areas have been abandoned and allowed to
regenerate (Chacón-Cascante et al. 2012).
The second priority area for future conservation efforts lies between
Arenal National Park and the Tenorio Complex, to the northeast east of
Lake Arenal. There are actually two potential corridors here: one along the
sub-corridor proposed in Moran et al. (2019) and another along the northern
shore of the Arenal reservoir. Both areas have relatively high forest cover and
fall within this important watershed for Costa Rican electricity production.
These areas are also sparsely populated (with the exception of La Fortuna
and adjacent communities), with most deforested lands devoted to cattle
ranching (MDM, personal observation) and almost no permanent crops or
human settlements (Fig. 2D).
The establishment of biological sub-corridors that extend outwards from
the existing protected areas of the MAB would conceivably be positive in
supporting populations of animals that need large areas for viable popu-
lations (Weber and Rabinowitz 1996; Crooks and Sanjayan 2006; Hilty et
al. 2012) and in helping some species survive the dispersal expected to be
necessary to adjust to climate change (Heller and Zavaleta 2009; Fung et al.
2017; Beita et al. 2021). The Bellbird Biological Corridor was created in part
to protect and improve habitat for altitudinal migrants, such as frugivorous
birds and some Lepidoptera (Welch et al. 2011; Newcomer et al. 2022). As
this analysis shows, land within and adjacent to this corridor also has high
value for many other ecosystem services, such as high biodiversity and soil
conservation on steep slopes. The proposed corridor between the MAB and
the Tenorio Complex would help to connect the protected areas of the Cor-
dillera de Tilarán (MAB) to protected areas in the Cordillera de Guanacaste
(with numerous important protected areas), which apparently have healthy
populations of Baird’s tapirs (Tapirus bairdii, Carbonell and González-Zúñiga
2000) and jaguars (Panthera onca, Montalvo et al. 2022), two species imper-
iled in Costa Rica. These two species are present in the MAB, but only at low
population densities (Zamzow et al. 2018) that are likely not viable in the
long-term. With the larger populations of tapirs in the Tenorio Complex and
jaguars across the Cordillera de Guanacaste into the tropical dry forests be-
yond (Calvo-Alvarado et al. 2009), a corridor connecting these areas to the
MAB would likely increase probabilities of survival for these species across
north-central Costa Rica.
A third potential area of focus, extending from the MAB to Juan Castro Blan-
co National Park, is more problematic. While the western part of the proposed
sub-corridor has abundant forested lands of high conservation value (Fig. 4),
the eastern portions comprise landscapes with comparatively low ecosystem
services and include extensive areas of pasture and cultivated lands (ornamen-
tal plants are a large industry in this region). Creating a functional biological

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Nature Conservation 58: 243–260 (2025), DOI: 10.3897/natureconservation.58.142210
Lindsay Stallcup et al.: Conservation priorities in a tropical forest
corridor in this area would, therefore, likely be expensive and logistically di-
cult. Considering economic limitations for land acquisition and other conser-
vation efforts, it would, therefore, be preferable to focus on the other two areas
mentioned above (Bellbird and Arenal-Tenorio).
The entire region falls within the Mesoamerican Corridor proposal (Miller et al.
2001), which extends from Panama to Mexico, with the jaguar (P. onca) as its ag-
ship species. Due to political instability and other social challenges throughout the
region, the creation of a functional mega-corridor remains a logistical challenge.
However, within Costa Rica, the completion of this corridor is more feasible, given
the large amount of land currently under protection, the historically strong con-
servation efforts country-wide and the long-term political stability of the country.
The opportunity to create benets for the local economy by ecotourism may also
foster the completion of the corridor in Costa Rica. There are only relatively small
gaps between large protected areas, so that a small, carefully targeted increase
in lands under conservation could potentially link all of Costa Rica’s major protect-
ed areas across the entire length of the country. Ultimately, if Costa Rica hopes
to preserve its rich biodiversity in perpetuity, this landscape-scale conservation
strategy is probably the best method. Fortunately, with the already extensive sys-
tem of public and private protected areas, along with focused efforts on remain-
ing lands that retain high conservation values, there is a good probability that
Costa Rica can continue to be a model for 21st century conservation.
Conclusions
This analysis shows that conservation efforts in the MAB have been successful
in creating a large complex of biodiverse protected areas. Yet these areas re-
main an island of protected lands isolated from larger regional protected areas
and several life zones remain completely unprotected. However, land of high
conservation value and low traditional economic value remains that, if placed
under conservation, could mitigate these two issues. Considering the incredi-
bly high contribution of this area to Costa Rica’s total biodiversity and the large
ecotourism economy dependent upon this biodiversity, we urge conservation
organisations to consider how to achieve expanded, but selective land con-
servation of the MAB, possibly through a combination of direct land purchase,
ecotourism development in these areas and cooperative agreements between
landowners and conservation organisations. Examples of direct land purchase
priorities might include some of the highest conservation priority areas of the
Bellbird Biological Corridor directly adjacent to protected areas and/or the
smaller unforested areas of the Tenorio Corridor that would, if reforested, con-
nect larger areas of forest together. However, since direct purchase of all high
conservation priority lands is nancially and logistically dicult, we expect that
cooperative work with private landowners will be the primary way to achieve
greater success in preserving the rich biodiversity of this region.
Acknowledgements
We wish to thank the Alex C. Walker Foundation for their generous funding for
this project. Peter Gausmann and João Pompeu provided valuable feedback
that improved this manuscript.

257
Nature Conservation 58: 243–260 (2025), DOI: 10.3897/natureconservation.58.142210
Lindsay Stallcup et al.: Conservation priorities in a tropical forest
Additional information
Conict of interest
The authors have declared that no competing interests exist.
Ethical statement
No ethical statement was reported.
Funding
This work was supported by Alex C. Walker Foundation.
Author contributions
Conceptualization: LS, MDM. Data curation: EM, DR. Formal analysis: EM, MDM, DR, LS.
Funding acquisition: MDM, LS. Investigation: LS. Methodology: LS, MDM. Project admin-
istration: LS. Software: EM, DR. Supervision: LS. Writing - original draft: MDM. Writing
- review and editing: LS, EM, MDM, DR.
Author ORCIDs
Matthew D. Moran https://orcid.org/0000-0002-8611-6092
Data availability
All of the data that support the ndings of this study are available in the main text.
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