Conference PaperPDF Available

Analysis of distribution of river dolphins (Inia and Sotalia) in protected and transformed areas in the Amazon and Orinoco basins

Authors:

Abstract and Figures

The South American river dolphins have evolved in the continental aquatic ecosystems of the Amazon, Grande, Iténez-Mamoré, Araguaia-Tocantis and Orinoco rivers. The spatial and temporal distribution and the habitat use of these cetaceans do in these systems, are determined by distinct environmental characteristics such as precipitation regimes, elevation, productivity and biomass specific to each system. In addition, geomorphological accidents, such as rapids, have emerged as barriers that separate dolphin populations, potentially promoting processes of speciation. To date, there is no comprehensive analysis of river dolphins distribution and representativeness in protected areas or areas transformed by hydroelectric plants. In the present work, through
Content may be subject to copyright.
!
1!
Analysis of distribution of river dolphins (Inia and
Sotalia) in protected and transformed areas in the
Amazon and Orinoco basins
!
Federico Mosquera-Guerra 1,2, Fernando Trujillo1, Danni Parks3, Marcelo Oliveira-da-
Costa4, Miriam Marmontel5, Dolors Armenteras-Pascual2, Saulo Usma4, Daphne Willems4,
Juan David Carvajal-Castro6, Hugo Mantilla-Meluk6, Nicole Franco1, Diego Amorocho4,
Roberto Maldonado4, Karina Berg4, Lila Sainz4, Paul A. Van Damme7, Elizabeth Cambell8.!
!
1 Fundación Omacha: Calle 84 No. 21 – 64 - Barrio el Polo - Bogotá, D.C,
Colombia. federico.mosqueraguerra@gmail.com!
!
2 Grupo de Ecología del Paisaje y Modelación de Ecosistemas-ECOLMOD: Departamento
de Biología, Universidad Nacional de Colombia - Cra 30 No. 45-03 - Bogotá D.C,
Colombia.!
!
3 Whitley Fund for Nature : 110 Princedale Road l - London W11 4NH, United Kingdom.!
!
4 WWF – Brazil; Bolivia; Colombia; Ecuador, Peru, Netherlands; Deutschland; United
Kingdom. Rue Mauverney, 28 1196 Gland, Switzerland
!
5 Mamiraguá: Estrada do Bexiga, 2.584 Bairro Fonte Boa Cx. Postal 38 69.553-225 – Tefé
(AM), Brasil.!
!
6 Universidad del Quindiìo: Programa de Biologiìa, Carrera 15 No. 12 Norte. Quindiìo -
Armenia - Colombia.!
!
7 Faunagua: Av. Max Fernández final s/n - Plazuela del Chillijchi (Arocagua) –
Cochabamba, Bolivia.!
!
8 Prodelphinus: Enrique Palacios 630 – 204, Lima 18 – Miraflores - Lima, Peru.!
!
!
!
Abstract
The South American river dolphins have evolved in the continental aquatic
ecosystems of the Amazon, Grande, Iténez - Mamoré, Araguaia - Tocantis and Orinoco
rivers. The spatial and temporal distribution and the habitat use of these cetaceans do in
these systems, are determined by distinct environmental characteristics such as
precipitation regimes, elevation, productivity and biomass specific to each system. In
addition, geomorphological accidents, such as rapids, have emerged as barriers that
separate dolphin populations, potentially promoting processes of speciation. To date, there
is no comprehensive analysis of river dolphins distribution and representativeness in
protected areas or areas transformed by hydroelectric plants. In the present work, through
!
2!
niche and spatial modeling tools, we research the representativeness of both protected areas
and areas transformed by hydroelectric plants in the Amazon and Orinoco basins in the
distribution of river dolphins (Inia and Sotalia). The models presented here were
constructed using the MaxEnt algorithm through the integration of 35,594 georeferenced
records and 19 environmental variables derived from the Bioclim and Hydroshed database,
which were parameterised in the R programme. A good representation of the distribution of
river dolphins within the protected areas was evidenced, although the limited management
of the aquatic ecosystems inside the protected areas does not guarantee the conservation of
these species. A major threat identified for river dolphins in South America is the loss of
habitat and fragmentation as a result of the construction of hydroelectric dams. We
examined the degree of overlap between the distribution of Inia and Sotalia and
hydroelectric projects in construction, operation and planning phases and provided an initial
quantification of this tensor. Finally, we consider that the cumulative impacts
(fragmentation, regulation of the flood pulse, retention of limiting nutrients and alteration in
the levels of productivity) generated by this type of infrastructure at the macrobasin scale
will exacerbate the level of the threats to the conservation of river dolphins and their
habitats in the Amazon and Orinoco basins.
Key words: Conservation,!distribution,!human!impact,!hydroelectric!dams,!
river dolphins.!
!
!
Introduction
The South American river dolphins are represented by the subspecies and species of
the genus Inia and Sotalia. They are widely distributed in the aquatic ecosystems of the
Amazon, Orinoco, Tocantins basins and Orinoco delta (Caballero et al. 2007; Reeves et al.
2011; Secchi et al. 2012; Carvajal-Castro et al. 2015; Caballero et al. 2017). Throughout
their distribution it has been identified that geological interruptions, particularly rapids, act
as effective barriers separating natural populations of river dolphins and promoting
processes of differentiation between populations (Rice 1998).
To date, three subspecies of Inia geoffrensis are recognized with distribution
throughout the Amazon basin (I. g. geoffrensis) and the Orinoco basin (I. g. humboldtiana)
with a suggested vicarious isolation caused by the formation of the Canal del Casiquiare on
the ecological border between the Colombian Orinoquia and the Venezuelan Amazon (Da
Silva & Martin 2000). I. g. boliviensis seems to have been isolated from I. g. geoffrensis
because of the 400 km of rapids from Porto Velho on the Madeira river to Riberalta on the
Beni river in Bolivia (Rice 1998). Currently the Bolivian bufeo (I. g. boliviensis) occurs in
the basin of the Madeira, Iténez and Grande river basins in Bolivia and Brazil (Trujillo et
al.1999; Banguera- Hinestroza et al. 2002; Ruiz-García et al. 2008; Ruiz-García 2010;
Reeves et al. 2011; 2013). However, the taxonomy for the genus Inia has been discussed
and even a new species has been described: the Araguaia river dolphin (Inia
araguaiaensis), present in the hydrographic complex formed by the Araguaia - Tocantins
rivers (Hrbek et al. 2014).
!
3!
The genus Sotalia includes two species based on cranial morphology and genetic
evidence (Madeira et al. 2004; Cunha et al. 2005; Caballero et al. 2007; 2010; 2017).
Sotalia guianensis (P-J. Van Bénedén 1864) presents populations distributed along the
coasts and estuaries of the Atlantic Ocean from Honduras to Brazil, and in the north of
South America, including individuals established in Lake Maracaibo, middle and delta
parts of the Orinoco river in Venezuela. Recent genetic studies determined that there is a
divergence of 600,000 years between continental and coastal populations (Carvajal-Castro
et al. 2015; Caballero et al. 2017). The species Sotalia fluviatilis (Gervais y Deville, In
Gervais 1853) is found in the Amazon river basin (riparian zone) and is sympatric with Inia
geoffrensis in Brazil, Colombia, Ecuador, Peru and French Guiana in the Amazon river
basin (Borobia et al. 1989; Da Silva 1994; Martin y Da Silva 2004; Cunha et al. 2005;
Caballero et al. 2007; Flores and Da Silva 2009; Trujillo et al. 2010; Secchi et al. 2012;
Carvajal-Castro et al. 2015; Caballero et al. 2017).
Although river dolphins are obligate aquatic mammals, external environment
variables external to this environment associated with the river basins they inhabit, such as
precipitation and atmospheric temperature, may be determining aspects of their ecology,
directly or indirectly affecting their occurrence in a particular area. Historically, the
Orinoco, Amazon and the Araguaia-Tocantins complexes have been identified as different
biogeographical and ecological units characterized by contrasting climatic conditions
(McClain and Naiman 2008; Edmond et al. 1996; WCS 2017). These deferring conditions
affect in many ways the hydric dynamics of their basins, determining the composition and
structure of the biota associated with the course of its main and tributary rivers. Despite
analyses of the potential influence that external variables may have on aquatic biota, to
date, there is no comprehensive analysis in the South American territory on the
representativeness of the distribution of river dolphins in protected areas or areas
transformed by hydroelectric plants.
New tecnological approaches based on Geographic Information Systems (GIS),
currently allow the characterisation of the availability of habitat for species in a given area
through suitability models at a regional scale. Regionally, ecological conditions such as
elevation, temperature and precipitation in combination with latitude, determine, among
others, the vegetation cover, which consequently at a local scale define aspects such as
productivity, nutrient flow and conductivity in the related water ecosystems at a local scale.
Although the relationship between regional and local variables has been studied relatively
poorly, GIS analysis opens a window of possibility to understand the distribution and
ecology of aquatic organisms such as river dolphins at the continental level.
In the present study, the results from river dolphin monitoring, based on sightings
are integrated with environmental information through niche modeling tools, with the
purpose of investigating the representativeness of the different species and subspecies in
protected areas and areas transformed by hydroelectric plants in the Amazon and Orinoco
basins.
!
4!
Material and Methods
Obtaining records and environmental variables
The environmental conditions included 19 bioclimatic variables from the Worldclim
database (Hijmans et al. 2005), in addition, radiation was obtained as an approximation of
primary productivity. To obtain this information, the values of the 12 months of the year
provided by Worldclim v.2 are averaged (Fick and Hijmans 2017). All the variables
presented a resolution of 30 arc-seconds (~1 km2 in Ecuador) (Table 1).
Table 1. Bioclimatic variables used in the potential distribution models of river dolphins
(Inia and Sotalia) in the Amazon and Orinoco river basins.!
Variables
Description
Elevation
Height in meters above sea level
Bio 1
Annual average temperature
Bio 2
Average daytime range (Mean of the month
(Max Temp - Min Temp))
Bio 3
Isothermality ((Bio 2/Bio 7) * 100)
Bio 4
Seasonality of temperature (Standard
deviation * 100)
Bio 5
Maximum temperatura of the hottest month
Bio 6
Minimum temperature of the coldest month
Bio 7
Annual temperature range (Bio 5 - Bio 6)
Bio 8
Average temperature of the wettest quarter
Bio 9
Average temperature of the driest quarter
Bio 10
Average temperature of the warmest quarter
Bio 11
Average temperature of the coldest quarter
Bio 12
Annual rainfall
Bio 13
Precipitation of the wettest month
Bio 14
Precipitation of the driest month
Bio 15
Seasonality of precipitation (Coefficient of
variation)
Bio 16
Precipitation of the wettest quarter
Bio 17
Precipitation of the driest quarter
Bio 18
Precipitation of the warmest quarter
Bio 19
Precipitation of the coldest quarter
Rad
Solar radiation
Potential distribution models
!
5!
The models of potential distribution of the subspecies and species of the genera Inia
and Sotalia were generated using the environmental variables and the georeferenced
records obtained through sightings in expeditions carried out within the framework of the
South American River Dolphin Conservation Programme (2006-2018) and the records
issued by river dolphins tagged with satellite telemetry in Colombia, Brazil and Bolivia
(Table 2, Figures 1& 2). The algorithm used was the maximum entropy (MaxEnt) (Phillips
et al. 2006). MaxEnt was chosen because it has been widely used and its best performance
has been demonstrated to estimate the potential distribution of the species more accurate
than other approaches (Graham and Hijmans 2006; Townsend et al. 2007). As MaxEnt only
works with information on the presence of species, it must generate pseudoausencias, more
appropriately called ‘background’ in order to obtain a calibration of the model (Phillips and
Dudík 2008). Therefore, 10000 randomly generated points (background) were used through
the northern zone of the Neotropic. 10 replicas were generated to perform an assembly
methodology (Araújo and New 2007) and thus obtaining a consensus model among the
replicas.
Table 2. Records of river dolphins (Inia and Sotalia) in the Amazon, Orinoco and
Tocantins-Araguaia river basins.
Georeferenced sightings
9.050
4.452
2.388
974
5.954
303
23.121
!
6!
Figure 1. Georeferenced records for genus Inia in South America.
Figure 2. Georeferenced records for genus Sotalia in South America.
!
7!
To evaluate the performance of the model, a "k fold partitioning" approach was
used, with an area under the receiver curve (AUC) as the evaluation metric, using 75% of
the occurrence data to perform modeling and 25% of the remaining occurrence data to test
the model. The AUC value is used to evaluate the discrimination ability of the model: AUC
values close to 1 are considered as a perfect prediction and values of 0.5 or less reflect that
the model is not better than a random model. These analyses were carried out using the R
software, using the dismo libraries (Hijmans et al. 2015), SDMTools (VanDerWal et al.
2014) and raster.
The consensus model generated by MaxEnt is a probability map, on which the
probability of the presence of species is shown. This probability map was used to make a
binary map representing the presence and absence of dolphins, establishing a threshold
value as a criterion, defined as the maximum sum of specificity and sensitivity (MSS).
Therefore, the probability values (probability map) that were equal to or greater than this
threshold value were considered as demostrating the presence of river dolphins (the value
of the pixel equal to 1); on the other hand, values below this threshold were considered as
species’ absence (pixel value equal to 0).
Representation of protected and transformed areas in the potential distribution of river
dolphins (Inia and Sotalia)
A statistical analysis was carried out overlapping the models of potential
distribution, with the protected areas (WDPA) (UNEP-WCMC 2010) downloaded from
(www.protectedplanet.net) and areas transformed by hydroelectric plants in Brazil, Bolivia,
Colombia, Ecuador, Peru and Venezuela (Anderson et al. 2018, Latrubesse et al. 2017).!The
number of pixels intersecting the distribution of species and protection zones were
quantified as an indirect measure of the ability of protected areas to protect dolphins.!At the
same time, the areas transformed by hydroelectric dam construction, operation and
planning in the Amazon, Orinoco and Araguaia-Tocantins basins were quantified in order
to demonstrate the impact of this type of infrastructure on river dolphin populations. For the
purpose of calculating these areas, the function of the library rgeos was used in the
statistical software R.
Results
Potential distribution models
The generated models demonstrate a high correlation, with AUC values of 0.8852
(I. g. geoffrensis), 0.889 (I. g. humboldtiana), 0.9189 (I. g. boliviensis), 0.9738 (I .
araguaiaensis), 0.948 (Sotalia fluviatilis) and 0.933 (S. guianensis). Figure 3 shows the
modelled potential distrubution of the South American river dolphin species and subspecies
(Inia and Sotalia).
!
8!
!
!
!
!
!
!
!
Figure 3. Modelled potential distrubution of the South American river dolphins (species and
subspecies) Inia and Sotalia, derived from the algoritm MaxEnt. A. I.g. geoffrensis. B. I.g.
humboldtiana. C. I.g.boliviensis. D. I. araguaiaensis. E. Sotalia fluviatilis. F. S. guianensis.
Representation of protected and transformed areas in the potential distribution of river
dolphins (Inia and Sotalia)
A
B
C
D
E
F
!
9!
Potential distribution areas for the South American river dolphins (Inia and Sotalia) and
their representation in the aquatic ecosystems in Amazon protected areas were calculated in
order to establish their representativeness for each taxa. (Table 3). In the category of
protected areas, strict figures were included, such as National Parks and regional parks, and
other figures such as sustainable reserves and Ramsar sites were included.
Table 3. Representativeness of protected areas in the distribution of South American river
dolphins (Inia and Sotalia).
Species
Total&area&
potential&
distribution&
Areas of aquatic ecosystems in conservation km2
Total&area&in&
Conservation&
km2&
Brasil
Bolivia
Colombia
Ecuador
Peru
Venezuela
I.g.geoffrensis
468.717!
69.324
!!
5.839
2.900
11.455
397
89.915 (19,2%)
I.g.humboldtiana
114.962!
!!
!!
2.151
!!
!!
10.634
12.785 (11,1%)
I.g.boliviensis
76.597
5.892
12.494
!!
!!
!!
!!
18.386 (24,0%)
I. araguaiaensis
76.182
11.503
!!
!!
!!
!!
!!
11.503 (15,1%)
S. fluviatilis
356.716!
54.892
!!
2.637
2.900
7.726
!!
68.155 (19,1%)
S. guianensis
17.473
!!
!!
!!
!!
!!
4.630
4.630 (26.5%)
Figure 4. Distribution of the genus Inia in Amazon protected areas
!
10!
Figure 5. Distribution of of the genus Sotalia in Amazon protected areas.
The areas transformed by hydroelectric plants were calculated in phases of planning,
construction and operation, and the representation of these in the potential distribution areas
of the South American river dolphins (Table 4).
Table 4. Representativeness of transformed areas by hydroelectric plants in the distribution
of South American river dolphins (Inia and Sotalia).
Species
Total&area&
potential&
distribution&
km2
Areas transformed by hydroelectric plants in
different phases km2
Operation
Constrution
Planning
I. g. geoffrensis
468.717
77.077 (16.4%)
68.995 (14.7%)
139.981 (29.9%)
I. g. humboldtiana
114.962
26.348 (22.9%)
6.302 (5.5%)
I.g. boliviensis
76.597
1.482 (1.9%)
I. araguaiaensis
76.182
41.853 (54.9%)
16.005 (21%)
36.281 (47.6%)
Sotalia fluviatilis
356.716
77.077 (21.6%)
68.995 (19.3%)
139.981 (39.2%)
Sotalia guianensis
17.473
2.704 (15.5%)
2.555 (14.6%)
!
11!
Figure 6. Spatialisation of habitats transformed by hydroelectics in the operation phase for
the genus Inia.
Figure 7.!Spatialisation of habitats transformed by hydroelectics in the constrution phase
for the genus Inia.
!
12!
Figure 8. Spatialisation of habitats transformed by hydroelectics in the planning
phase for the genus Inia.
Figure 9. Spatialisation of habitats transformed by hydroelectics in the operation phase for
the genus Sotalia.
!
13!
Figure 10. Spatialisation of habitats transformed by hydroelectics in the constrution phase
for the genus Sotalia.
Figure 11. Spatialisation of habitats transformed by hydroelectics in the planning
phase for the genus Sotalia.
Discussion
Potential distribution models
River dolphins (Inia and Sotalia) occur in the Amazon and Orinoco river basins,
from the deltas upstream, to where impassable rapids, waterfalls, lack of water and possibly
!
14!
low temperatures block their movement (Best and da Silva 1989a, b). For the genus Inia
three geographic populations have been recognised as subspecies: I. g. geoffrensis in the
Amazon basin, except for the Madeira basin in Bolivia upstream, from the Teotonio rapids,
I. g. boliviensis in the upper Madeira basin, and I. g. humboldltiana in the Orinoco basin
(Rice 1998, Reeves et al. 2011). Genetic studies reveal the relevance of these geographical
barriers in the generation of vicariant speciation processes, as is the case with Inia
araguaiaensis, a species recently described, whose populations are isolated by the
Araguaia-Tocantins hydrographic complex (Hrbek et al. 2014).
For I. g. geoffrensis, the distribution generated by the model coincide with the
distribution presented by de Best and da Silva (1989a), (1989b) and Leatherwood (1996),
who place its occurence in the rivers Xingu, Tapajós, Madeira (downstream from the rapids
of Teotonio), Purus, Juruá, Ucayali and Marañón (and Samiria tributary) that flow
generally towards the north, and the Negro river with itstributaries Caquetá (Japurá),
Apaporis, Putumayo (Iça) and Napo.
In relation to the distribution of I. g. humboldtiana, the model outcome matches
what was reported by Pilleri y Gihr (1977); Best y da Silva (1989a), (1989b); Meade and
Koehnken (1991); Velásquez-Roa et al. (2015), identifying the subspecies’ presence in the
Apuré tributaries (Portuguesa and Guanmar), Capanaparo, Cinaruco, Meta, Bita, Vichada,
Tomo, Tuparro, Guaviare (tributary Guayabero), Inírida and Atabapo (and Temi tributary)
that flow to the south and east, and the tributaries Aro, Caura, Parquaza, Ventauri (San Juan
tributary) that flow to the north and west, as well as the Casiquiare Canal, which connects
the Orinoco with the Negro river (a tributary of the Amazon), above and below the two
series of rapids in Puerto Ayacucho, which are the main barriers that are expected to
separate the dolphin populations of the Amazon and the Orinoco (Reeves et al. 2011).
Nevertheless, river dolphins have been seen crossing the first group of rapids in Puerto
Ayacucho (Atures) during the high tide (Fernando Trujillo, personal communication with
B.D. Smith).
The modelled distribution generated for Inia boliviensis coincides with what is
stated by Pilleri and Gihr (1977); Best and da Silva (1993); Aliaga-Rossel et al. (2006); Da
Silva (2009); Aliaga-Rossel (2010); Tavera et al. (2010); Cella-Ribeiro et al. (2013), and
Gravena et al. (2014), that this unique aquatic mammal is present in the sub-basins of the
rivers Abuna, Guaporé, Iténez or Guaporé basin (including Verde and Iporuporé
tributaries), Mamoré basin and its primary and secondary tributaries: Pirai, Grande, Ichilo,
Chapare, Ibaré, Tijamuchi, Apere, Yacuma and Yata, Beni (and Orton tributary); on the
Madeira river, its distribution is considered below the Tetonio rapids located upstream from
Porto Velho. According to Cella-Ribeiro et al. (2013), the Bolivian river dolphin presents
an estimated evolutionary divergence of 3.1 million years of genetic isolation generated by
the geographic barrier formed by a series of 18 rapids along a stretch of 290 kilometers on
the Madeira river. These rapids are thought to act as a barrier to the movement of dolphins
and thus restrict the distribution of I.g.boliviensis upstream of the rapids, and I.g.geoffrensis
downstream of the rapids.!
!
15!
This example is similar to the recent description of the species Inia araguaiaensis
(Hrbek et al. 2014) distributed in the Araguaia-Tocantins river hydrographic complex,
currently isolated from the Amazon river basin (Rossetti and Valeriano 2007; Goulding et
al. 2003). The two basins have been disconnected, although not completely isolated from
each other in the transition from Pliocene to Pleistocene (Rossetti and Valeriano 2007).
Currently, only a narrow channel west of the island of Marajo joins the delta of the Amazon
river with the Para river, which drains the Araguaia-Tocantins river. The connectivity
between the Araguaia-Tocantins and Amazon basins is restricted by a series of important
rapids in the lower Tocantins river, becoming an important biogeographical element to
generate speciation processes (Hrbek et al. 2014).
The results obtained in relation to the distribution of S. fluviatilis coincide with the
reports generated by Layne (1958); Obregón et al. (1988); Borobia et al. (1991); Trujillo
(1992), (1994a), (2000); Vidal et al. (1997); McGuiere and Henningsen (2007); Gómez-
Salazar et al. (2010); Carvajal-Castro et al. (2015) and Caballero et al. (2017). All report its
presence in the Amazon basin as far inland as southern Peru, eastern Ecuador and
southeastern Colombia. This presents a sympatric distribution with I. g.geoffrensis (Secchi
2012), although S. fluviatilis does not occur in the Beni/ Mamoré river basin ,in Bolivia nor
in the upper part of the Negro river (Flores y da Silva 2009). The results obtained by
modeling identy limitations for the distribution of S. fluviatilis in the Caqueta/Japura river
basin, determined by the rapid of Cordoba and reported by Trujillo (1994b); Trujillo
(1995), Galindo (1997); Trujillo et al. (2006); Gómez-Salazar et al. (2010); Pavanato et al.
(2014) and Caballero et al. (2017); in the Apaporis river, its distribution is limitated by the
rapids of Estrella and Puerco (Gómez-Salazar et al. 2010).
In relation to S. guianensis, the presence of the species in the Colombian Orinoco is
not corroborated, which suggests that its distribution is restricted to the middle basin and
delta of the Orinoco. This can be explained by the rapids of Maipures, Atures and the Dead
between the Ayacucho and Samariapo Ports in the Venezuelan Orinoco, probably
restricting the species’ distribution (Gómez-Salazar et al. 2010; Herrera-Trujillo 2012).
Representation of protected and transformed areas in the potential distribution of river
dolphins (Inia and Sotalia)
In the Amazon and Orinoco basins there are important areas under conservation
management, such as national natural parks and Ramsar sites. Among these, there are areas
of distribution of river dolphins (Trujillo et al. 2014). However, the remoteness of these
areas, the limited resources for their control and surveillance, the constant threat of
extractive economies such as gold mining, deforestation of riparian forest, commercial
fishing and directed catches, as well as the terrestrial approach of the initiatives of
conservation initiatives, make the management of aquatic ecosystems within protected
areas still limited (Mosquera-Guerra et al. 2015).
The transformation of the heterogeneous and complex aquatic ecosystems in the
Amazon through the construction of more than one hundred hydroelectric plants causes the
ecological homogenisation of these systems, changes in the flood pulses downstream of the
!
16!
dams and the retention of limiting nutrients for primary productivity in aquatic food webs
such as the N and P (Forsberg et al. 2017; Latrubesse et al. 2017; Anderson et al. 2018).
It also causes significant losses in fluvial connectivity exactly where the greatest diversity
of river dolphins and fish on the planet are found (Mosquera-Guerra et al. 2015; Anderson
et al. 2018).!These tensors have caused the transformation of extensive areas occupied by
river dolphins in South America. Arauho and Wang (2014), report the effects on
populations of I. araguaiaensis due to the presence of seven hydroelectric projects
constructed in their distribution area and for I.g. boliviensis, I.g. geoffrensis and Sotalia
fluviatilis are reported a total of three new ones.
!These effects are not only limited to the fragmentation of complex and
heterogeneous aquatic systems such as the Araguaia, Tocantins and Madeira rivers. These
ecosystems are made up of habitats types essential for feeding, reproduction and refuge of
dolphins such as confluences, tributaries, lakes and main rivers and tributaries with
different origins, Andean in the case of white waters, jungle in the black and clear rivers
influenced by the Brazil shield
Another type of cumulative negative effect at the macrobasin scale is reported by
Forsberg et al. (2017), which predicts that upon entry into operation of the Rositas dams,
Angosto Del Bala, Inambari, Tam 40, Pongo De Aguierre and Pongo De Monseriche, will
reduce the supply of sediment by 69%, phosphorus by 67% and nitrogen by 57% in the
Andean region and in the entire Amazon basin by 64, 51 and 23%, respectively. These
large reductions in the supply of sediments and nutrients will have a great impact on the
geomorphology of the channels, the fertility of the floodplains and the aquatic productivity
(Latrubesse et al. 2017).
These effects will be greater near the dams and will extend to the lowland flood
plains (Latrubesse et al. 2017). It is expected that the attenuation of the downstream flood
pulse will alter the survival, phenology and growth of the floodplain vegetation and reduce
the primary and secondary productivity of the floodplain food source for fish in its different
phases. This reduction in the biomass of these systems could potentially exacerbate the
conflicts between the river dolphins and the artisanal and commercial fisheries due to the
decrease of fishing resource in the Amazon.
When analyzing the representativeness of protected areas, it is evident that in the
case of Inia boliviensis and Inia araguiaensis it is relatively low. That is why it is advisable
to encourage the creation of aquatic ecosystem conservation figures that generate protection
mechanisms for these species. Ramsar sites with implemented management plans can be
efficient and suitable for river dolphins.
Acknowledgments
This research was conducted as part of the South America River Dolphins
Conservation Programme sponsored by Whitley Found for Nature, Foundation Segre,
WWF, Nature Serve and Colciencias. The authors thank the researchers and local and
national authorities who participated in the 28 expeditions carried out in South America and
satellite telemetry project to study the ecology of the movement of river dolphins in the
Amazon and Orinoco.
!
17!
References
Aliaga-Rossel, E., McGuire, T. L. and Hamilton, H. 2006. Distribution and encounter rates
of the river dolphin (Inia geoffrensis boliviensis) in the central Bolivian Amazon. Journal of
Cetacean Research Management 8(1): 87–92.
Aliaga-Rossel, E. and T. L. McGuire. 2010. Iniidae. pp. 535-549. In: Wallace, R.B., H.
Gómez, Z.R. Porcel & D.I. Rumiz (eds.) Distribución, Ecología y Conservación de los
Mamíferos Medianos y Grandes de Bolivia. Centro de Ecología y Difusión Simón I. Patiño,
Santa Cruz.
Anderson, E. P., Jenkins, C. N., Heilpern, S., Maldonado-Ocampo, J. A., Carvajal-Vallejos,
F. M., Encalada, A. C., Rivadeneira, J. F., Hidalgo, M., Cañas, C. M., Ortega, H., Salcedo,
N., Maldonado, M. 2018. Tedesco, Fragmentation of Andes-to-Amazon connectivity by
hydropower dams. Sci. Adv. 4, eaao1642.
Arauho, C and Wang, J. 2014. The dammed river dolphins of Brazil: impacts and
conservation. Fauna & Flora International, Oryx, 49(1), 17–24
doi:10.1017/S0030605314000362
Araujo, MB, New M. 2007. Ensemble forecasting of species distributions. Trends Ecol.
Evol. 22: 42–47.
Banguera-Hinestroza, E., Cárdenas, H., Ruiz- García, M., Marmontel, M., Gaitán, E.,
Vázquez, R., and García-Vallejo, F. 2002. Molecular identification of evolutionarily
significant un its in the Amazon River dolphin Inia sp. (Cetacea:Iniidae). Journal of
Heredity 93:312–322.
Best, R.C, da Silva VMF (1993). Inia geoffrensis. Mamm Species 426:1–8.
Best, R. C. and da Silva, V. M. F. 1989a. Amazon River dolphin, boto Inia geoffrensis (de
Blainville, 1817). In: S. H. Ridgway and R. Harrison (eds), Handbook of marine mammals,
Vol. 4: River dolphins and the larger toothed whales, pp. 1-24. Academic Press.
Best, R. C. and Da Silva, V. M. F. 1989b. Biology, status and conservation of Inia
geoffrensis in the Amazon and Orinoco river basins. In: W. F. Perrin, R. L. Brownell, K.
Zhou and Lu Jiankang (eds), Biology and conservation of the river dolphins, pp. 23-34.
IUCN Species Survival Commission.
Borobia, M., Siciliano, S., Lodi, L., and Hoek, W.1991. Distribution of the South American
dolphin Sotalia. Canadian Journal of Zoology 69 (4): 1025-1039 pp. http: / /
dx.doi.org/10.1139/z
Bivand R, Rundel C. 2014. rgeos: Interface to Geometry Engine–Open Source (GEOS). R
Package.
Caballero, S., Trujillo, F., Vianna, J.A., Barrios-Garrido, H., Montiel, M.G., Beltran-
Pedreros, S., Marmontel, M., Santos, M.C.O., Rossi-Santos, M.R., Santos, F.R. and Baker,
!
18!
C.S. 2007.Taxonomic status of the genus Sotalia: species level ranking for 'tucuxi' (Sotalia
fluviatilis) and 'costero' (Sotalia guianensis) dolphins. Marine Mammal Science 23(2): 358-
386. http://dx.doi.org/10.1111/j.1748-7692.2007.00110.x
Caballero, S., Trujillo, F., Vianna, J.A., Barrios-Garrido, H., Montiel, M.G., Beltrán
Pedreros, S., Marmontel, M., Santos, M.C.O., Rossi-Santos, M.R., Santos, F.R and Baker,
C.S. 2010. Mitochondrial DNA diversity, differentiation and phylogeography of the South
American riverine and coastal dolphins Sotalia fluviatilis and Sotalia guianensis. Latin
American Journal of Aquatic Mammals 8(1-2): 69-79.
http://dx.doi.org/10.5597/lajam00155
Caballero, S., Trujillo, F., Del Risco, A., Herrera, O., and Ferrer, A. 2017. Genetic identity
of Sotalia dolphins from the Orinoco River. Marine Mammal Science 33(4): 1214-1223.
http://dx.doi.org/10.1111/mms.12422
Carvajal-Castro, J.D., Velásquez-Roa, T., Mantilla-Meluk, H., Trujillo, F. and Mosquera-
Guerra, F. 2015. Modelación de nicho y aspectos biogeográfícos del género Sotalia
(Cetartiodactyla: Delphinidae) en los ríos Amazonas y Orinoco, Colombia. Momentos de
Ciencia. 12 (2). 121-125.
Cella-Ribeiro, A., G. Torrente-Vilara., D.B. Hungria., Oliveira M de. 2013. As corredeiras
do Rio Madeira. Peixes do Rio Madeira. pp 47–53.
Cunha, H.A., Da Silva, V.M.F., Laílson-Brito, J.J., Santos M.C.O., Flores, P.A.C., Martin,
A.R., Azevedo, A.F., Fragoso A.B.L., Zanelatto, R.C. and Solé-Cava, A.M. 2005. Riverine
and marine ecotypes of Sotalia fluviatilis are different species Marine Biology 148(2): 449-
457.http://dx.doi.org/10.1007/s00227- 005-0078-2
Da Silva V.M.F. 2009. Amazon River Dolphin (Inia geoffrensis). In: Perrin WF, Wursig B,
Thewissen JGM (eds) Encycl. Mar. Mamm. Academic Press, London, UK, pp 18–20.
Da Silva V. and A.R. Martin. 2000. The status of the boto or Amazon River dolphin Inia
geoffrensis (de Blainville, 1817): a review of available information. Paper submitted at the
meeting of the IWC Scientific Committee, 2000. IWC, Cambridge, UK.
Da Silva, V. M. F. and Best, R. C. 1994. Tucuxi Sotalia fluviatilis (Gervais, 1853). In: S. H.
Ridgway and R. Harrison (eds), Handbook of marine mammals, Volume 5 The first book
of dolphins. 43-69. Academic Press, London, UK.
Edmond J.M., Palmer, M.R., Measures, C.I., Brown, E.T. and Huh, Y. 1996. Fluvial
geochemistry of the eastern slope of the northeastern Andes and its foredeep in the drainage
of the Orinoco in Colombia and Venezuela. Geochimica et Cosmochimica Acta 60: 2949–
2976.
Fick, S.E., Hijmans, R.J. 2017. WorldClim 2: new 1km spatial resolution climate surfaces
for global land areas. International Journal of Climatology, 37(12), 4302-4315.
Flores, P.A.C. and Da Silva V.M.F. 2009. Tucuxi and Guiana Dolphin - Sotalia fluviatilis
and S. guianensis. 1188-1191pp. En: Perrin, W.F., Würsig, B. y Thewissen, J.G.M. (Eds)
Encyclopedia of Marine Mammals. 2nd ed. Academic Press, Amsterdam, Netherlands.
!
19!
Forsberg, B.R., Melack, J.M., Dunne, T., Barthem, R.B., Goulding, M., Paiva, R.C.D., et
al. 2017. The potential impact of new Andean dams on Amazon fluvial ecosystems. PLoS
ONE 12(8): e0182254. https://doi.org/10.1371/journal. pone.0182254
Galindo, A.1997. Ecología y abundancia de los delfines de río Inia geoffrensis y Sotalia
fluviatilis en el río Caquetá, área de influencia de la Pedrera, Colombia. B.Sc.Thesis.
Universidad del Valle. Cali. Colombia. 77 pp.
Goulding, M., Barthem, R.B., Ferreira, E.J.G. 2003. The Smithsonian Atlas of the Amazon.
Washington, DC: Smithsonian Institution Press.
Gómez Salazar, C., Portocarrero-Aya, M., Caballero, S., Bolaños-Jiménez, J., Utreras, V.,
McGuire, T., Ferrer-Pérez, A., Pool, M., and Aliaga-Rossel, E. 2010. Update on the
freshwater distribution of Sotalia in Colombia, Ecuador, Peru, Venezuela and Suriname.
LAJAM 8(1-2): 171-178 pp. E-ISSN 2236-1057 / ISSN 1676-7497
Graham, C., Hijmans, R.J. 2006. A comparison of methods for mapping species ranges and
species richness. Global Ecology and Biogeography, 578–587.
Gravena, W., Izeni, P.F., Da Silva, M.N.F., Da Silva, V.M.F., and Hrbek, T. 2014.
Looking to past and the future: were the Madeira River rapids a geographical barrier to the
boto (Cetacea: Iniidae)?. Conserv Genet. 15:619-629 pp. DOI 10.1007/S10592-014-0565-4
Herrera-Trujillo, O. 2012. Estatus de los delfines de río Sotalia sp. e Inia geoffrensis en la
cuenca del Orinoco. Tesis para optar al título de Máster Universitario en Biodiversidad en
Áreas Tropicales y su Conservación. Universidad Internacional de Melendéz-Pelayo. Quito
(Ecuador). 99 pp.
Hijmans, R.J., Cameron, S.E., Parra, J.L., Jones, P.G., Jarvis, A. 2005. Very high resolution
interpolated climate surfaces for global land areas.International journal of climatology,
25(15): 1965-1978.
Hijmans R.J. 2015. raster: Geographic Data Analysis and Modeling. R package version 2.4-
18. ver http://CRAN.R-project.org/package=raster
Hijmans, R.J., Phillips, S., Leathwick, J., Elith, J. 2015. dismo: Species Distribution
Modeling. R package version 1.0-12. ver http://CRAN.R-project.org/package=dismo
Hrbek, T., da Silva, V.M.F., Dutra, N., Gravena, W., Martin, A.R. and Farias, I.P. 2014. A
new species of river dolphin from Brazil or: how little do we know our biodiversity. PLoS
ONE 9(1): e83623. doi:10.1371/journal.pone.0083623
Latrubesse, E. M., E. Y. Arima, T. Dunne, T., .et al. 2017. Damming the rivers of the
Amazon basin. Nature 546(7658):363-369.
Layne, J. 1958. Observations on freshwater dolphins in the upper Amazon. Journal of
Mammalogy 39(1): 1-22. http:/ / dx.doi.org/10.2307/ 1376605
!
20!
Leatherwood, S. 1996. Distributional ecology and conservation status of river dolphins
(Inia geoffrensis and Sotalia fluviatilis) in portions of the Peruvian Amazon. Thesis, Texas
A&M University.
Madeira Di Beneditto, A.P. and Arruda Ramos, R.M. 2004. Biology of the marine tucuxi
dolphin (Sotalia fuviatilis) in south-eastern Brazil. J. Mar. Biol. Ass. U.K. 84,1245-1250.
Martin, A.R., Da Silva, V.M.F. and Salmon, D.L. 2004. Riverine habitat preferences of
botos (Inia geoffrensis) and tucuxis (Sotalia fluviatilis) in the Central Amazon. Marine
Mammal Science 20: 189-200.
Meade, R. H. and Koehnken, L. 1991. Distribution of the river dolphin, tonina Inia
geoffrensis, in the Orinoco river basin of Venezuela and Colombia. Interciencia 16: 300-
312.
McClain M.E. and R.J. Naiman. 2008. Andean Influences on the Biogeochemistry and
Ecology of the Amazon River. Oxford Journals. Oxford University Press. BioScience, Vol.
58, No. 4: 325-338.
McGuire, T.L., and Henningsen, T. 2007. Movement Patterns and Site Fidelity of River
Dolphins (Inia geoffrensis and Sotalia fluviatilis) in the Peruvian Amazon as Determined
by Photo-Identification. Aquatics Mammals. 33(3), 359-367 pp. DOI:
10.1578/AM.33.3.2007.359
Mosquera-Guerra, F., Trujillo, F., Diazgranados, M. C. and Mantilla-Meluk, H.. 2015.
Conservación de delfines de río (Inia geoffrensis y Sotalia fluviatilis) en los ecosistemas
acuáticos de la Amazonia y Orinoquia en Colombia. Momentos de Ciencia 12(2):77-86.
Obregón, C., Torres, F., and Trujillo, F. 1988. Colombian dolphins. Whalewatcher 22:21
pp.
Pavanato, H.J., Melo-Santos, G., Lima, D.S., Portocarrero-Aya, M., Paschoalini, M.,
Mosquera, F., Trujillo, F., Meneses, R., Marmontel, M., Maretti, C. 2016. Risks of dam
construction for South American river dolphins: a case study of the Tapajós River.
Endangered Species Research Endang Species Res. Vol. 31: 47–60, 2016 doi:
10.3354/esr00751
Pilleri, G. and Gihr, M. 1977. Observations on the Bolivian (Inia geoffrensis d'Orbigny,
1834) and the Amazonian bufeo (Inia geoffrensis de Blainville, 1817), with a description of
a new subspecies (Inia geoffrensis humboldtiana). Investigations on Cetacea 8: 11-76.
Phillips, S.J., Anderson, R.P., Schapire, R.E. 2006. Maximum entropy modeling of species
geographic distributions. Ecological Modelling. 190: 231–259.
Phillips, S.J., Dudík, M. 2008. Modeling of species distributions with Maxent: new
extensions and a comprehensive evaluation. Ecography. 31(2): 161-175.
Reeves, R.R., Jefferson, T.A., Karczmarski, L., Laidre, K., O’Corry-Crowe, G., Rojas-
Bracho, L., Secchi, E.R., Slooten, E., Smith, B.D., Wang, J.Y. and Zhou, K. 2011. Inia
!
21!
geoffrensis. The IUCN Red List of Threatened Species 2011: e.T10831A3220342.
http://dx.doi.org/10.2305/IUCN.UK.2011-1.RLTS.T10831A3220342.en. Downloaded on
30 March 2018.
Reeves, R.R. et al. 2013. Inia geoffrensis. The IUCN Red List of Threatened Species 2013:
e.T10831A3220342. http://dx.doi.org/10.2305/IUCN.UK.2011-1.RLTS.T10831A3220342.
.en. Downloaded on 30 March 2018.
Rice D.W. 1998. Marine mammals of the world: systematics and distribution. Society for
Marine Mammalogy, Special Publication Number 4 (Wartzok D, ed.), Lawrence, KS. USA.
Rossetti D de F, Valeriano M.M .2007. Evolution of the lowest Amazon basin modeled
from the integration of geological and SRTM topographic data.Catena 70: 253–265.
doi:10.1016/j.catena.2006.08.009.
Ruiz-García M, S. Caballero, M. Martínez- Agüero and J. Shostell. 2008. Molecular
differentiation among Inia geoffrensis and Inia boliviensis (Iniidae, Cetacea) by means of
nuclear intron sequences. Pages 177–223 in V.P. Koven, ed. Population genetics research
progress. Nova Science Publishers, Inc., Hauppauge, NY.
Ruiz-García, M. 2010. Changes in the demographic trends of Pink River Dolphins (Inia) at
the microgeographical level in Peruvian and Bolivian rivers and within the Upper Amazon:
Microsatellites and mtDNA analyses and insights into Inia’s origin. Pages 225–258 in M.
Ruiz-García y J. Shostell, eds. Biology, evolution, and conservation of river dolphins
within South America and Asia: Unknown dolphins in danger. Nova Science Publishers,
Inc., Hauppauge, NY.
Secchi, E. 2012. Sotalia fluviatilis. The IUCN Red List of Threatened Species 2012:
e.T190871A17583369.http://dx.doi.org/10.2305/IUCN.UK.2012.RLTS.T190871A1758336
9.en. Downloaded on 30 March 2018.
Tavera, G., ER. Aliaga-Rossel., P.A. Van Damme,, A. Crespo. 2010. Distribution and
conservation status of the Bolivian river dolphin Inia boliviensis (d’Orbigny 1832). In:
Trujillo F, Crespo E, van Damme PA, Usma JS (eds) Action Plan South Am. River
Dolphins 2010-2020. WWF, Fundación Omacha, WDS, WDCS, Solamac, Bogota´, D.C.,
Colombia, pp 99–122.
Townsend P.A., Papeş, Eaton.M. 2007. Transferability and model evaluation in ecological
niche modeling: a comparison of GARP and Maxent. Ecography, 30, 550– 560.
Tchounwou, P.B., Ayensu, W.K., Ninashivili, N., Sutton, D. 2003. Enviromental exposure
to mercury and its toxicopathologic implications for public health. Environ Toxicol.
18:149-175.
Trujillo, F. 1992. Estimación poblacional de las especies dulceacuícolas de delfines de río
Inia geoffrensis y Sotalia fluviatilis en el sistema lacustre de Tarapoto y El Correo,
!
22!
Amazonía Colombiana. Special Report. Vol. 49. Centro de Investigaciones Científicas.
Universidad Jorge Tadeo Lozano, Bogotá D.C., Colombia.
Trujillo, F. 1994a. The use of photo-identification to study the Amazon River Dolphin, Inia
geoffrensis, in the Colombian Amazon. Marine Mammal Science 10 (3): 348-353 pp.
Trujillo, F. 1994b. Informe técnico de la Expedición Inia 94. Fundación Omacha. Bogotá,
D.C. 154pp.
Trujillo, 1995. Aspectos del comportamiento y la distribución de Inia geoffrensis y Sotalia
fluviatilis en el río Caquetá, Colombia. Special Report. Vol. 71. Centro de investigaciones
Científicas, Universidad Jorge Tadeo Lozano. Bogotá D.C., Colombia.
Trujillo, F., M.C. Diazgranados and L. Fuentes. 1999. Manual para la identificación de
Mamíferos Acuáticos. Fundación Omacha. 161p.
Trujillo, F. 2000. Habitat use and social behaviour of the freshwater dolphin Inia
geoffrensis (de Blainville 1817) in the Amazon and Orinoco basins. Ph.D. Thesis.
Aberdeen University. Scotland. 157 pp.
Trujillo, F., Diazgranados, M.C., Galindo, A and Fuentes, L. 2006. Delfón gris Sotalia
fluviatilis. Pp 273-278. En: Rodriguez-M.J.V., Alberico, M., Trujillo, F y Jorgenson, J. Eds.
2006. Libro Rojo de los Mamíferos de Colombia Serie Libros Rojos de Especies
Amenazadas de Colombia. Conservación Internacional y Ministerio de Ambiente, Vivienda
y Desarrollo Territorial. Bogotá D.C. Colombia.
Trujillo, F., Crespo, E., Van Damme, P. and J.S. Usma. 2010. The action plan for south
american river dolphins 2010 – 2020. WWF, WCS, Solamac, Fundación Omacha, 1-249.
Trujillo, F., Caicedo, D., and Diazgranados, M.C (Eds.). 2014. Plan de acción nacional para
la conservación de los mamíferos acuáticos de Colombia (PAN mamíferos Colombia).
Ministerio de Ambiente y Desarrollo Sostenible, Fundación Omacha, Conservación
Internacional y WWF. Bogotá D.C. 54 p.
UNEP-WCMC. 2010. Data Standards for the World Database on Protected Areas, UNEP-
WCMC.1–9.
VanDerWal J, Falconi L, Januchowski S, Shoo L, Storlie C. 2014. SDMTools: Species
Distribution Modelling Tools: Tools for processing data associated with species
distribution modelling exercises. R package version 1.1-221. Ver http://CRAN.R-
project.org/package=SDMTools
Velásquez-Roa, T., Carvajal-Castro, J.D., Mantilla-Meluk, H., Trujillo, F and Mosquera-
Guerra, F. 2015. Caracterización ecológica de cuencas utilizadas por el delfín rosado Inia
geoffrensis en Colombia, a través de modelamiento de nicho. Momentos de Ciencia. 12(2).
Pp: 126-130. ISSN 1692-5491
!
23!
Vidal, O., Barlow, J., Hurtado, L., Torre, J., Cendon, P., and Ojeda, Z. 1997. Distribution
and abundance of the Amazon River Dolphin (Inia geoffrensis) and the Tucuxi (Sotalia
fluviatilis) in the upper Amazon River. Marine Mammal Science 13(3) 427:445pp. http:/ /
dx.doi.org/10.1111/j.1748-7692.1997.tb00650.x
WCS (Wildlife Conservation Society) . 2017. http://aguasamazonicas.org/la-iniciativa/
... In the case of river dolphins, methods for estimating density and population size have stratified the river into habitat types, where perceived gradients in densespecific habitats exist [20,21]. However, seasonal variations of habitats along river courses due to the natural hydro-geomorphological evolution of a river basin [22,23] or due to human interference (e.g., dams for irrigation or hydroelectric power production, mining processes, intense fishing exploitation, cattle raising, and climate change) can change river landscapes [24][25][26][27][28] and cause shifts in patterns of dolphin distribution. ...
... The baiji (Lipotes vexillifer) is thought to be probably Extinct (EX) in the wild due to the same conditions that still-living river dolphins face. Bycatch, direct, and intentional catches, contamination by mercury, habitat and population fragmentation by water infrastructure projects (mainly dams), water chemical pollution, acoustic pollution, intense boat traffic, poorly managed tourism, and decline of prey diversity and abundances result in substantial short-term effects with limited knowledge of impact scales at the population level [5,25,27,28,36,37]. ...
... The importance of population parameters such as the density and population size of boto and tucuxi have already been addressed by several authors as crucial information to understand their ecology, as well as the effect of anthropogenic activities on their survival [1][2][3][4][5]12,13,20,21,25,27,28,30,31]. The aggregation of boto and tucuxi in specific habitats in the river system, their seasonal movements following water level variability and prey migration, and also a preliminary investigation of population size differences across river basins were examined by such studies. ...
Article
Full-text available
The dolphins Inia geoffrensis-boto and Sotalia fluviatilis-tucuxi are threatened cetaceans inhabiting river ecosystems in South America; population numbers are still lacking for many areas. This paper provides density and abundance estimations of boto and tucuxi in 15 rivers sampled during the past nine years as part of a multinational research alliance. Visual boat-survey data collection protocols and analyses have been developed since 2012 (based on Distance Sampling methods) and recently reviewed (2019) to improve robustness and comparability. Differences across the sampled rivers and the analyzed river basins (Amazon and Orinoco) pointed to a density/population size gradient with lower densities and abundances observed in the Orinoco basin (0.9-1.5 ind./km²), passing through the eastern Amazon basin (2-5 ind./km²), and the largest numbers found at the central Brazilian Amazon (lower Purus River-2012 (14.5 boto/km², N = 7672; 17.1 tucuxi/km², N = 9238)). However, in other parts of the central Amazon, the density of dolphins was smaller than expected for high productive whitewater rivers (1-1.7 ind./km² in the Japurá and Solimões rivers). We attributed these differences to specific features of the basin (e.g., hydro-geomorphology) as well as to the cumulative effects of anthropogenic activities. Citation: Paschoalini, M.; Trujillo, F.; Marmontel, M.; Mosquera-Guerra, F.; Paitach, R.L..; Pavanato, H.J.; Melo-Santos, G.A.; Van Damme, P.A.; Coelho, A.G.A..; Escobar-WW, M.; et al. Density and Abundance Estimation of Amazonian river
... The species is considered among the most threatened aquatic mammals globally (Reeves et al. 2003;Trujillo et al. 2010). Population decline is a result of cumulative effects caused by (1) bycatch and targeted killing because of fisheries conflict or consumption of their meat (Trujillo et al. 2010;Mintzer et al. 2016Mintzer et al. , 2018Williams et al. 2016;da Silva et al. 2018;Brum et al. 2021;Martin and da Silva 2021;Mosquera-Guerra et al. 2022); (2) habitat degradation resulting from timber exploitation, agricultural expansion, and gold mining (Mosquera-Guerra et al. 2019a, b); (3) death of individuals due to an increase in the number of stranding events caused by climate variability resulting from the negative effects of climate change (Mosquera-Guerra et al. 2019a); and (4) fragmentation of populations due to construction of hydropower dams, particularly in Bolivia, Brazil and Peru (Pavanato et al. 2016;Mosquera-Guerra et al. 2018;Anderson et al. 2019;Brum et al. 2021;Pivari et al. 2021). ...
... The areas evaluated were 247 km 2 for the Colombian Amazonas River and 428 km 2 in the Orinoco basin. These areas were defined through the previously monitored Amazon River dolphin populations (abundance estimates and satellite monitoring of six individuals, Gómez-Salazar et al. 2012;Mosquera-Guerra et al. 2018, 2019aTrujillo et al. 2019;Mosquera-Guerra et al. 2021; see Table 1 and S1). ...
Article
Full-text available
Context Identifying the habitat preferences and core areas of Inia geoffrensis activity is essential to designing effective strategies for the management and conservation of Amazon River dolphins and their habitats in the Colombian Amazonas River and Orinoco basin. Objectives Quantify the differential use of habitat that Amazon River dolphins exhibit and identify core areas of activity during seasons of rising waters in the Colombian Amazonas River and five major rivers in the Orinoco basin. Methods Based on processed satellite images from Landsat 8 (2018–2021), we classified habitat types used by I. geoffrensis as reported in the literature as follows: (1) main river, (2) confluences, (3) tributaries, (4) channels, (5) islands, (6) bays, and (7) lagoons. We combined this dataset with GPS location data obtained from 17 tagged Amazon River dolphins to quantify the proportion of habitat types used. We used kernel density estimate (KDE) analysis to identify both areas used (K95) and core areas (K50) in the habitat types for the satellite-monitored individuals. Results Satellite tracking of I. geoffrensis individuals reported 16,098 locations classified into seven habitat types. For the analyzed period (rising waters) main habitat types used were as follow: (1) main river (n = 9144, 57%); (2) confluences (n = 932, 6%); (3) tributaries (n = 1423, 9%); (4) channels (n = 1597, 10%); (5) islands (n = 738, 5%); (6) bays (n = 1096, 7%), and (7) lagoons (n = 1168, 7%). Home range size (K95) for the satellite-monitored I. geoffrensis individuals ranged from 6 to 116 km² (mean = 40 ± 33); and the largest core areas (K50) or core area of activity were recorded in the main river, confluences, channels, bays, lagoons, and tributaries. Conclusions Our results demonstrated the importance of spatial ecology analysis of Amazon River dolphins for the definition of protected areas, quantifying the use of ecosystems within these areas, and the location of priority areas for the implementation of management plans for the species and habitats.
... et al., 2018;. In addition, the populations of this top predator of aquatic food webs (Goḿez-Salazar et al., 2011) and regulator of the structure and composition of fish populations (da Silva, 1983;Best and da Silva, 1989) are being threatened by the degradation of their habitats by tensors like the following: (1) construction and operation of 307 dams in the Amazon basin, 10 in Tocantins basin, and four in the Orinoco basin, (2) mining, (3) high rates of deforestation and fire in flood plains, and (4) the negative effects of climate change on the flood pulse (Mosquera- Guerra et al., 2018;Anderson et al., 2019;Mosquera-Guerra et al., 2019a;Mosquera-Guerra et al., 2019b;Campbell et al., 2020;Armenteras et al., 2021;Barbosa et al., 2021;Brum et al., 2021;Fearnside et al., 2021;Pivari et al., 2021). In this context, Amazon River dolphins are considered among the most threatened aquatic mammals globally (Reeves et al., 2003;Trujillo et al., 2010). ...
... habitat types used by Amazon River dolphins (e.g., confluences, channels, tributaries and lagoons) that are influenced by the ecology of the species and environmental aspects of the basin, such as: (1) wide variations in the home range sizes (K 95 = 6.2 -234 km², mean = 59 ± 13.5 km²), and core area sizes (K 50 = 0.6 -54.9 km², mean = 9 ± 2.6 km ²), (2) broad and specific habitat uses, (3) movements influenced by the lateral and longitudinal migration of fish, (4) sexual segregation of Inia individuals, and (5) ecological characteristics of the aquatic systems where they occur (productivity levels; Mosquera-Guerra et al., 2021). Although Inia spp. is distributed over >1,000,000 km 2 of the Amazon, Orinoco, and Tocantins basins, its occurrence is represented by only 15% of their distribution inside protected areas (Mosquera-Guerra et al., 2018). This is evidence that Inia spp. ...
Article
Full-text available
Unsustainable fisheries practices carried out in large parts of the Amazon, Tocantins, and Orinoco basins have contributed to the decline in the populations of the Amazon River dolphins (Inia spp.), considered Endangered by the International Union for Conservation of Nature (IUCN). Amazon River dolphin byproducts are often obtained through unregulated fisheries and from stranded and incidentally caught individuals that are traded for the flesh and blubber used for Calophysus macropterus fisheries, traditional and other medicinal purposes, and more recently for human consumption. To identify localities of use of Amazon River dolphins, we conducted a systematic review of the related literature published since 1980, complemented with structured surveys of researchers that allowed the identification of 57 localities for uses of Inia (33 in the Amazon, two in the Tocantins, and 22 in the Orinoco basins), and two more on the Brazilian Atlantic coast, with recent reports of targeted consumption in the upper Orinoco River. Subsequently, the localities of use or bushmeat markets where Amazon River dolphin byproducts are trafficked were identified. This information was integrated with a kernel density analysis of the distribution of the Inia spp. populations establishing core areas. Our spatial analysis indicated that the use of Inia spp. is geographically widespread in the evaluated basins. It is urgent that decision-makers direct policies towards mitigating the socioeconomic and cultural circumstances associated with illegal practices affecting Amazon River dolphin populations in South America. Keywords: amazon basin, Inia spp, artisanal fisheries, conservation, fishery-dolphin interactions, intentional catches, orinoco basin, tocantins basin
... Amazon River dolphins are considered top predators in freshwater ecosystems with a wide trophic spectrum (at least 43 species in 30 fish families); in average, adult river dolphins in the genus Inia consume 2.5-3.0 kg day -1 (Best and da Silva 1989). These predators are intrinsically dependent on the flood pulse dynamics of the basin and its effect on the temporal and spatial distribution of their prey (Mosquera-Guerra et al. 2018b). Species in these two genera perform longitudinal migrations, with differential spatial ecology between males and females. ...
... Species in these two genera perform longitudinal migrations, with differential spatial ecology between males and females. Males can have displacements of more than 400 km (Mosquera-Guerra et al. 2018b), whereas females are philopatric, remaining in wetlands where they reproduce and take care of their offspring (Trujillo 2000;Mosquera-Guerra et al. 2018b). River dolphin pregnancy lasts between 12.3 and 13 months, with 3.62 and 4.56 years between births. ...
Article
Full-text available
In the Amazon and Orinoco basins, mercury has been released from artisanal and industrial gold mining since the Colonial time, as well as a result of deforestation and burning of primary forest, that release natural deposits of methyl mercury, affecting the local aquatic vertebrate fauna. This study reports the presence of mercury in river dolphins’ genera Inia and Sotalia. Mercury concentrations were analysed in muscle tissue samples collected from 46 individuals at the Arauca and Orinoco Rivers (Colombia), the Amazon River (Colombia), a tributary of the Itenez River (Bolivia) and from the Tapajos River (Brazil). Ranges of total mercury (Hg) concentration in muscle tissue of the four different taxa sampled were: I. geoffrensis humboldtiana 0.003–3.99 mg kg⁻¹ ww (n = 21, Me = 0.4), I. g. geoffrensis 0.1–2.6 mg kg⁻¹ ww (n = 15, Me = 0.55), I. boliviensis 0.03–0.4 mg kg⁻¹ ww (n = 8, Me = 0.1) and S. fluviatilis 0.1–0.87 mg kg⁻¹ ww (n = 2, Me = 0.5). The highest Hg concentration in our study was obtained at the Orinoco basin, recorded from a juvenile male of I. g. humboldtiana (3.99 mg kg⁻¹ ww). At the Amazon basin, higher concentrations of mercury were recorded in the Tapajos River (Brazil) from an adult male of I. g. geoffrensis (2.6 mg kg⁻¹ ww) and the Amazon River from an adult female of S. fluviatilis (0.87 mg kg⁻¹ ww). Our data support the presence of total Hg in river dolphins distributed across the evaluated basins, evidencing the role of these cetaceans as sentinel species and bioindicators of the presence of this heavy metal in natural aquatic environments.
... Nat. 43(167):199-211, abril-junio de 2019Anderson, et al., 2018;Mosquera-Guerra, et al., 2018). Este tipo transformación de los ecosistemas acuáticos heterogéneos y complejos, especialmente en la Amazonia y la cuenca del Tocantins, como resultado de la construcción de más de un centenar de centrales hidroeléctricas provoca la homogeneización ecológica de estos sistemas, cambios en los pulsos de inundación aguas debajo de las represas, así como la retención de nutrientes como el nitrógeno y el fósforo, que limitan la productividad primaria en redes tróficas acuáticas (Forsberg, et al., 2017;Latrubesse, et al., 2017;Anderson, et al., 2018;Mosquera-Guerra, et al., 2018b). ...
... Estos tensores han causado la transformación de extensas áreas ocupadas por los delfines de río en Suramérica. Arauho & Wang, (2014) señalaron los efectos que tendría en la población de la especie recientemente descrita I. araguaiaensis (Hrbek, et al., 2014), la presencia de siete proyectos hidroeléctricos, entre estos la hidroeléctrica de Tucuruí, los cuales transformarían el 54,9% de su área de distribución y restringirían los movimientos de la especie a tramos entre estos proyectos (Mosquera-Guerra, et al., 2018). Por otra parte, las especies I. boliviensis, I.g. ...
Article
Full-text available
En el presente estudio se emplearon los tamaños poblacionales de dos géneros de delfines de río (Inia y Sotalia) como indicadores del estado de salud de 23 ecosistemas acuáticos asociados con las cuencas de los ríos Amazonas y Orinoco. La información se recopiló durante 30 expediciones científicas realizadas entre el 2006 y el 2017 en Colombia, Ecuador, Perú, Bolivia, Brasil y Venezuela. Los resultados evidenciaron procesos de degradación ecosistémica en los ríos Caquetá, Putumayo, Iténez y Grande en la cuenca del Amazonas, y en el Tocantins- Araguaia, el Guaviare y la cuenca alta del Orinoco. Esta condición puede verse incrementada en las próximas décadas debido a la pérdida de conectividad entre los Andes y el Amazonas por la presencia de 142 hidroeléctricas ya existentes y 160 que están en fase de planeación y han sido propuestas para los ríos que drenan desde las cabeceras andinas al Amazonas. Los impactos ecosistémicos en las redes tróficas acuáticas de estos sistemas generados por este tipo de infraestructura se han estudiado poco. Los resultados del estudio aportan importantes elementos para entender los procesos de degradación ocasionados por la fragmentación y la pérdida de la conectividad fluvial en la Amazonia y la Orinoquia a partir de los tamaños poblacionales de los delfines de río. Estos cetáceos tienen variados requerimientos ecológicos y se han adaptado evolutivamente a los cambios estacionales predecibles. Estas características ecológicas convierten a los delfines de río en excelentes indicadores para entender las afectaciones en los pulsos de inundación y sus efectos sobre la funcionalidad ecosistémica de los complejos sistemas hidrográficos de las cuencas del Amazonas y el Orinoco. © 2019. Acad. Colomb. Cienc. Ex. Fis. Nat.
... River dolphins are among the most endangered cetaceans in the world. The Amazon, Orinoco, Tocantins basins ( fig. 1) face severe threats based in anthropic activities, ranging from bycatch (Reeves et al. 2003;Alves et al. 2012;Trujillo et al. 2010b;Iriarte and Marmontel 2013), deliberate killing as a bait (Iriarte and Marmontel 2014), loss of connectivity of the rivers because dam construction (Pavanato et al. 2016;Mosquera-Guerra et al. 2018;Gravena et al. 2014), deforestation, mercury pollution (Mosquera-Guerra et al. 2015 and2018a) and climate change (Trujillo et al. 2010). Additionally the tourism as dolphin watching and swimming/directly feeding is increasing in the Amazon region and is another concern for the conservation of the species. ...
... As Mosquera-Guerra et al. (2015 and2018a) evidence the presence of mercury (Hg) in dolphins' tissues in the Amazon and Orinoco basins, this may represent a threat to local populations of those species. Although there have not been studies of the effects of this heavy metal on river dolphins (Inia and Sotalia) in South America, there are evaluations with marine mammals (e.g. ...
Conference Paper
Full-text available
River dolphins are among the most endangered cetaceans in the world. The Amazon, Orinoco, Tocantins basins (fig. 1) face severe threats based in anthropic activities, ranging from bycatch (Reeves et al. 2003; Alves et al. 2012; Trujillo et al. 2010b; Iriarte and Marmontel 2013), deliberate killing as a bait (Iriarte and Marmontel 2014), loss of connectivity of the rivers because dam construction (Pavanato et al. 2016; Mosquera- Guerra et al. 2018; Gravena et al. 2014), deforestation, mercury pollution (Mosquera- Guerra et al. 2015 and 2018a) and climate change (Trujillo et al. 2010). Additionally the tourism as dolphin watching and swimming/directly feeding is increasing in the Amazon region and is another concern for the conservation of the species.
... The species is considered among the most threatened aquatic mammals globally (Reeves et al. 2003;Trujillo et al. 2010). Population decline is a result of cumulative effects caused by (1) bycatch and targeted killing because of fisheries conflict or consumption of their meat (Trujillo et al. 2010;Mintzer et al. 2016Mintzer et al. , 2018Williams et al. 2016;da Silva et al. 2018;Brum et al. 2021;Martin and da Silva 2021;Mosquera-Guerra et al. 2022); (2) habitat degradation resulting from timber exploitation, agricultural expansion, and gold mining (Mosquera-Guerra et al. 2019a, b); (3) death of individuals due to an increase in the number of stranding events caused by climate variability resulting from the negative effects of climate change (Mosquera-Guerra et al. 2019a); and (4) fragmentation of populations due to construction of hydropower dams, particularly in Bolivia, Brazil and Peru (Pavanato et al. 2016;Mosquera-Guerra et al. 2018;Anderson et al. 2019;Brum et al. 2021;Pivari et al. 2021). ...
Article
Full-text available
Context Identifying the habitat preferences and core areas of Inia geoffrensis activity is essential to design- ing effective strategies for the management and conservation of Amazon River dolphins and their habitats in the Colombian Amazonas River and Orinoco basin. Objectives Quantify the differential use of habitat that Amazon River dolphins exhibit and identify core areas of activity during seasons of rising waters in the Colombian Amazonas River and five major rivers in the Orinoco basin. Methods Based on processed satellite images from Landsat 8 (2018–2021), we classified habitat types used by I. geoffrensis as reported in the literature as follows: (1) main river, (2) confluences, (3) tributaries, (4) channels, (5) islands, (6) bays, and (7) lagoons. We combined this dataset with GPS location data obtained from 17 tagged Amazon River dolphins to quantify the proportion of habitat types used. We used kernel density estimate (KDE) analysis to identify both areas used (K95) and core areas (K50) in the habitat types for the satellite-monitored individuals. Results Satellite tracking of I. geoffrensis individuals reported 16,098 locations classified into seven habitat types. For the analyzed period (rising waters) main habitat types used were as follow: (1) main river (n=9144, 57%); (2) confluences (n=932, 6%); (3) tributaries (n=1423, 9%); (4) channels (n=1597, 10%); (5) islands (n=738, 5%); (6) bays (n=1096, 7%), and (7) lagoons (n = 1168, 7%). Home range size (K95) for the satellite-monitored I. geoffrensis individuals ranged from 6 to 116 km2 (mean=40±33); and the largest core areas (K50) or core area of activity were recorded in the main river, confluences, channels, bays, lagoons, and tributaries. Conclusions Our results demonstrated the importance of spatial ecology analysis of Amazon River dolphins for the definition of protected areas, quantifying the use of ecosystems within these areas, and the location of priority areas for the implementation of management plans for the species and habitats. Keywords Amazonas River · Habitat use · Home range · Kernel density · Orinoco Basin · Spatiotemporal distribution · Satellite telemetry
Article
Full-text available
Resumen Eventos evolutivos ocurridos en el mioceno medio (16 millones de años) divergieron a los delfines de río suramericanos y asiáticos de sus ancestros oceánicos dando lugar a cuatro géneros de delfines de río: Platanistoidea: i) Inia (Amazonas, Orinoco y Araguia-Tocantis); ii) Platanista (Ganges y Brahmaputra), y el ecológicamente extinto iii) Lipotes (Yangté) y Delphinoidea; iv) Sotalia (Amazonas, Orinoco y Ara-guia-Tocantis). Objetivo: Establecer y consolidar información científica acerca de estas especies que permita orientar efectivamente las acciones de manejo y conservación de sus poblaciones y hábitats. Metodología: Se realizó una búsqueda sistemática de publicaciones relacionadas con delfines de río en aspectos como: i) evolución-filogenia, ii) conservación, iii) comportamiento, iv) reproducción, v) planes de manejo-guías de avistamiento, vi) ecología del movimiento, vii) hábitat y viii) estudios poblacionales. Resultados: Se observó un aumento del número de publicaciones desde 2009, siendo Brasil (24,4%, n=57) y Colombia (13,4%, n=32) los países que mayormente contribuyen al conocimiento de delfines de río. La categoría con el mayor número de publicaciones es la conservación (39%, n=85), los cuales han contribuido a los planes de manejo (6,4%, n=14). Por último, la especie mejor estudiada es I. geoffrensis con 40,6% (n=110) y la menor representada es P. g. minor con 4,4% (n=12). Conclusión: Es importante establecer el estado de conocimiento genético de los diversos taxones suramericanos que permita dilu-cidar su taxonomía; por otro lado, en Asia, la subespecie P. g. minor no presenta un plan de manejo para la conservación de la especie, además de un escaso conocimiento acerca de su ecología. Abstract Evolutionary events in the medium Miocene (16 years million) diverged to the dolphin's river in South Ame-rica and Asia of its oceanic ancestors giving place to four genera of river dolphins: Platanistoidea: i) Inia (Amazonas, Orinoco, and Araguia-Tocantis), ii) Platanista (Ganges and Brahmaputra), and it the ecologically extinct iii) Lipotes (Yangté), and Delphinoidea: iv) Sotalia (Amazonas, Orinoco, and Araguia-Tocantis). Objective: Establish and combine scientific search about these species that allow orient effectively the management actions and conservation of their population and habitats. Methodology: For this one was made a systematic search of publications related to river dolphins in aspect as i) evolution-phylogeny, ii) conservation, iii) behavior, iv) reproduction, v) management plans-sighting guides, vi) movement ecology , vii) habitat, viii) population studies. Results: It was observed increase in the number of publications since 2009, being Brasil (24.4%, n=57) and Colombia (13.4%, n=32) the country's that mostly contribute the study of river dolphins. The category that most is studied is the conservation (39%, n=85), which has contributed to the management plans (6.4%, n=14). Finally, the species with more studies is I. geoffrensis with 40.6% (n=110) and the minor represented is P. g. minor with 4.4% (n=12). Conclusion: Is necessary to set up the state of knowledge genetic of the diverse taxon's South Americans that allow explaining your
Book
Full-text available
Trujillo, F., Caicedo, D., Diazgranados, M.C. & I.C. Avila. (2022). Plan de Acción Nacional para la Conservación de los Mamíferos Acuáticos de Colombia 2022-2035. In: Avello-Castiblanco, G.C., González-Delgadillo, A.M., Quintero-Gil, J.A. (Eds.) Ministerio de Ambiente y Desarrollo Sostenible, Bogotá, DC. Colombia. 96p. ISBN: 978-958-5551-82-4.
Article
Full-text available
Increased energy demand has led to plans for building many new dams in the western Amazon , mostly in the Andean region. Historical data and mechanistic scenarios are used to examine potential impacts above and below six of the largest dams planned for the region, including reductions in downstream sediment and nutrient supplies, changes in downstream flood pulse, changes in upstream and downstream fish yields, reservoir siltation, greenhouse gas emissions and mercury contamination. Together, these six dams are predicted to reduce the supply of sediments, phosphorus and nitrogen from the Andean region by 69, 67 and 57% and to the entire Amazon basin by 64, 51 and 23%, respectively. These large reductions in sediment and nutrient supplies will have major impacts on channel geomorphology, flood-plain fertility and aquatic productivity. These effects will be greatest near the dams and extend to the lowland floodplains. Attenuation of the downstream flood pulse is expected to alter the survival, phenology and growth of floodplain vegetation and reduce fish yields below the dams. Reservoir filling times due to siltation are predicted to vary from 106–6240 years, affecting the storage performance of some dams. Total CO 2 equivalent carbon emission from 4 Andean dams was expected to average 10 Tg y-1 during the first 30 years of operation, resulting in a MegaWatt weighted Carbon Emission Factor of 0.139 tons C MWhr-1. Mercury contamination in fish and local human populations is expected to increase both above and below the dams creating significant health risks. Reservoir fish yields will compensate some downstream losses, but increased mercury contamination could offset these benefits.
Article
Full-text available
Although dolphins are entirely aquatic mammals, non-aquatic environmental variables associatedwith the basins they inhabit, such as precipitation and temperature, are likely to determine someaspects of their ecology directly affecting the species occurrence in a particular area. For Colombia, twosubspecies of Inia geoffrensis are thought to be distributed across the eastern lowlands of the Orinoquia(Inia geoffrensis humboldtiana) and Amazon (Inia geoffrensis geoffrensis). Across the distribution of thegenus, geographic features such as rapids have been claimed as barriers separating naturalpopulations generating vicariant events; it is possible that contrasting ecologies are reinforcing adifferentiation, and promoting speciation. Up to date, there is no a comprehensive analysis on theecological differentiation among basins inhabited by the two pink dolphin subspecies present inColombian. In this work, we investigate the ecological differences between these two subspecies by theniche modeling. Models were built using the MaxEnt algorithm, through the integration of 8435dolphin sights (I. g. geoffrensis N= 3592 and I. g. humboldtiana N= 4843), and 22 environmental variablesderived from the Bioclim e Hydroshed datasets, and parameterized in the program R. Areas of highsuitability for pink dolphins, released by our models, were congruent with previously proposeddistribution for the two subspecies in Colombia and were strongly supported by the area under thecurve metric (AUC 0,985). Our results suggest an ecological differentiation among the basins occupyby the two subspecies of pink dolphins. Globally, we conclude that external factors are part of theecological differentiation between I. geoffrensis subspecies for the analyzed basins.
Article
Full-text available
More than a hundred hydropower dams have already been built in the Amazon basin and numerous proposals for further dam constructions are under consideration. The accumulated negative environmental effects of existing dams and proposed dams, if constructed, will trigger massive hydrophysical and biotic disturbances that will affect the Amazon basin’s floodplains, estuary and sediment plume. We introduce a Dam Environmental Vulnerability Index to quantify the current and potential impacts of dams in the basin. The scale of foreseeable environmental degradation indicates the need for collective action among nations and states to avoid cumulative, far-reaching impacts. We suggest institutional innovations to assess and avoid the likely impoverishment of Amazon rivers.
Article
Full-text available
We created a new dataset of spatially interpolated monthly climate data for global land areas at a very high spatial resolution (approximately 1 km 2). We included monthly temperature (minimum, maximum and average), precipitation, solar radiation, vapour pressure and wind speed, aggregated across a target temporal range of 1970–2000, using data from between 9000 and 60 000 weather stations. Weather station data were interpolated using thin-plate splines with covariates including elevation, distance to the coast and three satellite-derived covariates: maximum and minimum land surface temperature as well as cloud cover, obtained with the MODIS satellite platform. Interpolation was done for 23 regions of varying size depending on station density. Satellite data improved prediction accuracy for temperature variables 5–15% (0.07–0.17 ∘ C), particularly for areas with a low station density, although prediction error remained high in such regions for all climate variables. Contributions of satellite covariates were mostly negligible for the other variables, although their importance varied by region. In contrast to the common approach to use a single model formulation for the entire world, we constructed the final product by selecting the best performing model for each region and variable. Global cross-validation correlations were ≥ 0.99 for temperature and humidity, 0.86 for precipitation and 0.76 for wind speed. The fact that most of our climate surface estimates were only marginally improved by use of satellite covariates highlights the importance having a dense, high-quality network of climate station data.
Chapter
Full-text available
Online http://www.santoantonioenergia.com.br/peixesdoriomadeira/