Research Article |
Corresponding author: Francisco Javier Sahagún-Sánchez ( francisco.sahagun@cucea.udg.mx ) Corresponding author: Octavio Rojas-Soto ( octavio.rojas@inecol.mx ) Academic editor: William Magnusson
© 2024 Alejandra Galindo-Cruz, Francisco Javier Sahagún-Sánchez, Fabiola López-Barrera, Octavio Rojas-Soto.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Galindo-Cruz A, Sahagún-Sánchez FJ, López-Barrera F, Rojas-Soto O (2024) Recent changes in tropical-dry-forest connectivity within the Balsas Basin Biogeographic Province: potential effects on endemic-bird distributions. Nature Conservation 55: 177-199. https://doi.org/10.3897/natureconservation.55.120594
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Maintaining landscape connectivity is a conservation priority for biodiversity as it may mitigate the adverse effects of forest degradation, fragmentation, and climate change by facilitating species dispersal. Despite their importance for biodiversity conservation, Mexican tropical dry forests (TDFs) face high fragmentation rates due to anthropogenic activities. In this study, we analyzed the connectivity dynamics of TDFs in the Balsas Basin Biogeographic Province (BBBP) between 2013 and 2018, focusing on old-growth and secondary TDF covers, including Protected Areas and Important Bird Areas. We evaluated the effects of connectivity loss and gain on the distribution areas of 30 endemic bird species with ecological associations with TDFs in the BBBP. We found expansion in TDFs accounting for a total increase of 227,905 ha due to secondary forest increase (12%). In contrast, old-growth forests experienced a reduction of 66,576 ha in the study area (8%). We also found a decrease in areas with high and very-high connectivity, coupled with an increase in low connectivity, except for TDFs inside Protected Areas, which increased by 3,000 ha, leading to higher connectivity. There was an increase in total forest cover in 27 species’ potential distribution, highlighting the possible role of secondary forests in promoting connectivity between old-growth forest patches. Our results reveal the complex dynamics between forest types, connectivity, and bird-species distributions. Despite an overall increase in forested areas, most TDFs continue to have low connectivity, likely impacting biodiversity, particularly for species that rely on highly conserved ecosystems. This study underscores the importance of integrated conservation strategies considering connectivity, forest recovery, and the dynamics of species-ecosystem interactions.
conservation priorities, important bird areas, old-grow forests, protected areas, secondary forests
Natural forests face severe threats due to degradation, destruction, and fragmentation, significantly impacting biodiversity worldwide (
Connectivity loss is a critical problem affecting biodiversity, as it hinders species’ long-distance movements, making it difficult for them to survive in the face of anthropogenic pressures (
Tropical dry forests (TDFs) rank among the world’s most endangered ecosystems, having lost nearly 80% of their original cover (
The BBBP holds eight Protected Areas (PAs;
Located in the states of Guerrero, Jalisco, México, Michoacán, Morelos, Oaxaca, and Puebla, the Balsas Basin Biogeographic Province (BBBP) covers nearly 7,640,000 ha (Fig.
Location of the Balsas Basin Biogeographic Province in México, showing the two adjacent provinces Trans-Mexican Volcanic Belt (light purple), and Sierra Madre del Sur (light blue); the more intense colors (gray scale) represent the higher altitudes.
The BBBP remains as an important area covered by tropical dry forests (TDFs) (
The selection of avian species for this study was based on the following criteria: 1) species endemic to México (
Endemic-bird species considered in this study. Degree of species specialization to Tropical dry forest (TDF-S), and forest dependency (FD): 3 = high, 2 = medium, 1 = low; Sensitivity to disturbance (Snts): h = high, m = medium, l = low; Feeding guild: c = carnivores, f = frugivores, g = granivores, i = insectivores, n = nectarivores.
Family | Species | TDF-S | FD | Snts | Feeding Guild |
---|---|---|---|---|---|
Cracidae | Ortalis poliocephala | 3 | 2 | l | f |
Odontophoridae | Philortyx fasciatus | 2 | 1 | l | g |
Cuculidae | Piaya mexicana | 2 | 2 | l | i |
Apodidae | Streptoprocne semicollaris | 2 | 2 | l | i |
Trochilidae | Calothorax pulcher | 1 | 2 | m | n |
Phaeoptila sordida | 2 | 2 | l | n | |
Cynanthus auriceps | 2 | 1 | l | n | |
Ramosomyia viridifrons | 1 | 1 | m | n | |
Saucerottia beryllina | 2 | 2 | m | n | |
Strigidae | Megascops seductus | 2 | 3 | m | i,c |
Glaucidium griscomi | 3 | 2 | m | i,c | |
Trogonidae | Trogon citreolus | 3 | 1 | l | f,i |
Picidae | Melanerpes chrysogenys | 2 | 1 | l | i |
Melanerpes hypopolius | 1 | 1 | l | f | |
Tityridae | Pachyramphus uropygialis | 1 | 2 | m | i |
Tyrannidae | Xenotriccus mexicanus | 1 | 2 | m | i |
Grallariidae | Grallaria ochraceiventris | 1 | 3 | h | i |
Furnariidae | Lepidocolaptes leucogaster | 2 | 3 | m | i |
Vireonidae | Vireo hypochryseus | 3 | 2 | m | i |
Troglodytidae | Pheugopedius felix | 2 | 2 | l | i |
Thryophilus sinaloa | 3 | 2 | l | i | |
Mimidae | Melanotis caerulescens | 2 | 1 | m | i,f |
Turdidae | Catharus occidentalis | 1 | 2 | m | i,f |
Turdus rufopalliatus | 2 | 1 | l | f | |
Turdus assimilis | 2 | 3 | m | f,i | |
Passerellidae | Peucaea humeralis | 2 | 2 | m | i |
Peucaea acuminata | 1 | 1 | l | g | |
Melozone kieneri | 2 | 2 | l | g | |
Cardinalidae | Passerina leclancherii | 2 | 1 | l | g |
Thraupidae | Sporophila torqueola | 1 | 1 | l | g |
To produce the Species Distribution Models (SDMs), we used the Maximum Entropy (MaxEnt) algorithm (
We evaluated model performance by calculating the Area Under the Curve (AUC) (
We used vector layers of land use and vegetation cover Series V (
To estimate connectivity between TDFs patches in the BBBP, we used the “Conefor Sensinode 2.6” program (
To identify the impact of connectivity changes over time, we quantified three different features: 1) the connectivity variation between old-growth and secondary forest covers, 2) the connectivity shifts impacting the distribution of each bird species and the overall bird richness, and 3) the connectivity alterations within PAs and IBAs (
Within the study area, TDFs experienced an increase from 44% to 47%, which represents a net expansion of 227,905 ha between 2013 and 2018 (Fig.
Old-growth and secondary tropical dry forests (TDF) dynamics based on
In 2013, most TDFs within the study area were classified in the lower-connectivity classes, covering a significant portion of the total area (Table
Tropical dry forests (TDFs) area per connectivity class. We present the type of forest cover, years, connectivity class in ha, and the percentage shown in parentheses.
Forest type | Year | Connectivity class | ||||
---|---|---|---|---|---|---|
Very High | High | Moderate | Low | Very Low | ||
Old-growth | 2013 | 194,747 (6) | 144,665 (4) | 57,099 (2) | 113,539 (3) | 331,945 (10) |
2018 | 187,235 (5) | 41,529 (1) | 153,384 (5) | 131,422 (4) | 261,848 (7) | |
Secondary | 2013 | 371,907 (11) | 58,758 (2) | 215,823 (6) | 803,335 (24) | 1,055,976 (32) |
2018 | 452,725 (13) | 70,662 (2) | 409,067 (11) | 713,312 (20) | 1,154,516 (32) | |
Total | 2013 | 566,654 (17) | 203,423 (6) | 272,922 (8) | 916,874 (27) | 1,387,921 (42) |
2018 | 639,960 (17) | 112,191 (3) | 562,451 (16) | 844,734 (24) | 1,416,364 (40) |
In 2013, forest fragments in the western and central regions of the BBBP had higher connectivity than the rest of the TDFs in the study area, which had “moderate” to “very low” connectivity (Fig.
Classes of the Integral Index of Connectivity for 2013 (1) and 2018 (2) A old-growth forest cover B secondary-forest cover C overall TDF cover.
Comparison of the distribution map of the analyzed bird species with the TDF-cover dynamics (including loss, gain, and stable covers), showed that only three of the thirty species in this study (Sporophila torqueola, Turdus assimilis, Vireo hypochryseus) decreased total forest cover within their distribution areas between 2013 and 2018, but, the variation in connectivity change within the range of each species was closely linked to their reliance on old-growth or secondary-forest cover (Suppl. material
Number of species that increased, remained stable, or decreased their distribution range within the different connectivity classes in the Tropical Dry Forests (TDFs) of the Balsas Basin Biogeographic Province from 2013 to 2018.
Connectivity class | TDF cover | Increase | Persistence | Decrease |
---|---|---|---|---|
Very high | Old-growth | 9 | 4 | 17 |
Secondary | 20 | 0 | 10 | |
Total | 18 | 0 | 12 | |
High | Old-growth | 2 | 15 | 13 |
Secondary | 7 | 2 | 21 | |
Total | 7 | 2 | 21 | |
Moderate | Old-growth | 0 | 1 | 29 |
Secondary | 27 | 1 | 2 | |
Total | 21 | 2 | 7 | |
Low | Old-growth | 23 | 1 | 6 |
Secondary | 5 | 0 | 25 | |
Total | 7 | 0 | 23 | |
Very low | Old-growth | 20 | 0 | 10 |
Secondary | 26 | 0 | 4 | |
Total | 27 | 0 | 3 |
Example of net change in species distribution area (DA) and percentage of DA for each connectivity class. Connectivity classes are very low (VL), low (L), moderate (M), high (H), and very high (VH). The effect of the change was classified as positive (+), and negative (-) for each forest cover type and overall connectivity.
According to the endemic-bird-richness map (Fig.
Endemic bird species richness contrasted with the connectivity classes of old-growth forest A 2013 B 2018 C. PAs: Protected Areas and IBAs: Bird Important Areas location within the Balsas Basin Biogeographic Province.
We recorded an increase of 3,000 ha of TDFs inside PAs from 2013 to 2018. However, there are many changes in the forest dynamics inside PAs. We observed an increase of 27,723 ha in areas with "very high" connectivity. The area expanded from 79,098 ha in 2013 to 106,821 ha in 2018. This growth was particularly noticeable in old-growth forests, which experienced an increase of 59,163 ha (Table
Dynamics of the tropical dry forests (TDFs) cover inside protected areas (PAs), and in the important bird areas (IBAs). We give the connectivity class, TDF cover type: old-growth, secondary, and both (Total), and the extent (ha) for 2013, 2018 and the balance from 2013 – 2018 in the Balsas Basin Biogeographic Province.
Connectivity Class | Forest cover type | PAs (ha) | IBAs (ha) | ||||
---|---|---|---|---|---|---|---|
2013 | 2018 | Balance | 2013 | 2018 | Balance | ||
Very high | Total | 79,098 | 106,821 | 27,723 | 94,447 | 130,307 | 35,860 |
Old-growth | 42,026 | 101,275 | 59,249 | 20,214 | 79,719 | 59,505 | |
Secondary | 37,072 | 5,546 | -31,525 | 74,233 | 50,588 | -23,645 | |
High | Total | 95,370 | 36,207 | -59,163 | 102,122 | 39,221 | -62,901 |
Old-growth | 95,370 | 36,207 | -59,163 | 97,143 | 39,221 | -57,922 | |
Secondary | – | – | – | 4,979 | – | -4,979 | |
Moderate | Total | 75,808 | 127,601 | 51,793 | 76,417 | 136,556 | 60,139 |
Old-growth | 52,510 | 77,811 | 25,300 | 21,560 | 40,249 | 18,689 | |
Secondary | 23,298 | 49,790 | 26,492 | 54,857 | 96,307 | 41,450 | |
Low | Total | 75,949 | 35,530 | -40,419 | 111,369 | 88,501 | -22,869 |
Old-growth | 30,305 | 6,583 | -23,723 | 29,061 | 20,132 | -8,930 | |
Secondary | 45,643 | 28,947 | -16,696 | 82,308 | 68,369 | -13,939 | |
Very low | Total | 98,536 | 121,807 | 23,271 | 196,529 | 198,241 | 1,712 |
Old-growth | 27,200 | 31,633 | 4,433 | 49,888 | 46,321 | -3,567 | |
Secondary | 71,336 | 90,175 | 18,838 | 146,641 | 151,920 | 5,279 |
In this study, we found evident changes in old-growth and secondary tropical dry forests (TDFs), especially in the north-central BBBP. Concurrently, there was an increase in secondary forests throughout the study area (Fig.
Nevertheless, this growth in secondary forests might be a short-term increase since other researchers, such as
In the BBBP, poorly connected old-growth TDFs predominate; however, the growth of secondary forests and the regeneration of forests with characteristics similar to old-growth forests from secondary patches led to an increase in the area covered with high connectivity in certain regions. In this sense, promoting the maintenance of remaining old-growth forest patches and encouraging passive forest restoration or natural regeneration can improve the overall connectivity of the landscape and mitigate fragmentation effects (
Bird communities, including a variety o diverse of guilds and forest dependency levels, are influenced in distinct ways by the age of forest succession, structural characteristics, and landscape variables (
The effectiveness of the Protected areas (PAs) network largely depends on its ability to address the connectivity and dispersal requirements of a diverse range of species (
Some IBAs may play a crucial role in expanding the PA network and are significant to bird conservation efforts (
Tropical dry forests of the BBBP showed changes in their structural connectivity between 2013 and 2018. The old-growth forests in the study area have lost 8% of their original cover; conversely, the coverage of secondary forests has increased by 10%. Also, our results revealed a landscape of changing forest connectivity within the BBBP and its implications for endemic bird species. In some cases, the increase in secondary forests favored connectivity among patches of old-growth forest and thus may reduce the potential adverse effects on bird populations. However, differences in landscape connectivity remain a challenge in maintaining biodiversity. Adaptive management practices may be needed to maintain connectivity and increase the quality of secondary forests for species dependent on tree species typical of old-growth forests.
We thank the National Council for Science and Technology in México (CONAHCyT) for the doctoral scholarship (grant number 855494), and the INECOL Bioclimatology Lab, especially Mauricio Díaz Vallejo, Daniel Valencia Rodríguez, Sebastian Forero Rodríguez for comments on the MS final version, and Claudio Mota Vargas for help with MS preparation. Additionally, we want to thank Clarice Matos and other two anonymous reviewers who contributed to this MS with thoughtful, constructive, and precise, comments and suggestions towards improving our manuscript.
The authors have declared that no competing interests exist.
No ethical statement was reported.
We thank the National Council for Science and Technology in México (CONAHCyT) for the doctoral scholarship (grant number 855494).
Conceptualization: ORS, FJSS, AGC. Data curation: AGC. Formal analysis: FJSS, AGC, FLB. Investigation: AGC, FLB, ORS. Methodology: FLB, ORS, AGC, FJSS. Supervision: ORS, FJSS. Validation: FJSS, AGC. Visualization: AGC. Writing - original draft: AGC, ORS, FJSS. Writing - review and editing: FLB.
Alejandra Galindo-Cruz https://orcid.org/0000-0001-7470-1449
Francisco Javier Sahagún-Sánchez https://orcid.org/0000-0002-4532-7539
Fabiola López-Barrera https://orcid.org/0000-0002-6092-6230
Octavio Rojas-Soto https://orcid.org/0000-0002-0201-1454
All of the data that support the findings of this study are available in the main text or Supplementary Information.
Information related to the species used as study case
Data type: pdf
INEGI’s vegetation covers grouped to be included in the Tropical Dry Forest class
Data type: pdf
Net change in area and total species range percentage for each connectivity class.
Data type: pdf