Thresholds of freshwater biodiversity in response to riparian vegetation loss in the Neotropical region

Brito J.G., Roque F.O., Martins R.T., Nessimian J.L., Oliveira V.C., Hughes R.M., de Paula F.R., Ferraz S.F., Hamada N.

Generally, habitat loss and fragmentation negatively affect biota, often in nonlinear ways. Such nonlinear responses suggest the existence of critical limits for habitat loss beyond which taxa experience substantial changes. Therefore, we identified change points for aquatic macroinvertebrate assemblages at both local-riparian and catchment extents in response to a forest-loss gradient in agriculture-altered landscapes of 51 small (1st to 3rd Strahler order) eastern Amazon streams. We used Threshold Indicator Taxa Analysis (TITAN) to identify change points for individual taxa and segmented regression analysis for assemblage richness. Considering the patterns of the cumulative frequency distributions of sum(Z−) maxima across bootstrap replications, peak changes in macroinvertebrate assemblages were at ∼9% (5–95 percentiles = 1–15%) of forest-loss at the catchment extent, and at ∼1.4% (5–95 percentiles = 0–35%) of forest-loss at the local-riparian extent. Although the assemblage change point at the site extent was less than that detected at the catchment extent, the markedly lower percentile range indicates that biotic assemblages are more clearly responsive to forest-loss at the catchment/network-riparian extents than the site extent. For catchment and site extents, segmented regression analysis determined a change point for assemblage richness at 57% and 79% of forest-loss, respectively. This indicates the low capacity of total richness to separate early and synchronous decreases of sensitive taxa from gradual increases of tolerant taxa. Our results also show that it is not enough to focus management and conservation actions on riparian zones, but that conservation strategies should be expanded to entire catchments as well. The sharp decline of sensitive taxa in response to removal of a small portion of forest cover, even at catchment extents, indicates that the Brazilian Forest Code is insufficient for protecting stream macroinvertebrates. Consequently, we recommend strategies to reverse the potential collapse of aquatic biodiversity, particularly through avoiding deforestation and forest degradation, encouraging socio-economic incentives for restoring degraded areas, creating protected areas, and maintaining the current protected areas. We argue that reducing habitat loss should be a top priority for conservation planners in tropical forests because the sensitivity of aquatic biodiversity to removal of riparian forest-cover in Amazon rainforests is higher than previously thought. Therefore, the Forest Code regulatory framework needs complementary regulation that may be achived by more restrictive State and biome policies.

Sone J.S., Gesualdo G.C., Zamboni P.A., Vieira N.O., Mattos T.S., Carvalho G.A., Rodrigues D.B., Alves Sobrinho T., Oliveira P.T.

We assess whether a Payments for Ecosystem Services (PES) programme met its objectives of reducing soil erosion and yielding water in an environmental protected area, the Guariroba River Basin, Midwestern Brazil. We measured rainfall and water discharge throughout 2012 and 2016. During the same period, soil and water conservation practices were performed in the basin, such as: building level terraces and riparian vegetation recovery. We separated streamflow into baseflow and direct runoff, then we evaluted the baseflow index that indicated that groundwater significantly contributes to total flow. Therefore, to investigate the effects on streamflow, we performed a trend analysis in the baseflow time series using the Mann-Kendall test. In addition, we analysed the efficiency of soil erosion regulation practices over time, considering the total payment and the trends found in the baseflow. Whereas precipitation records present a decreasing trend (1 mm month-1), baseflow tends to increase by 0.018 m3 s-1 in the same period. Our findings show that soil conservation practices performed in the basin increase baseflow and also provide a better resilience to endure extreme events such as drought based on an increase in forest areas and soil conservation practices such as level terrace.

Azevedo-Santos V.M., Frederico R.G., Fagundes C.K., Pompeu P.S., Pelicice F.M., Padial A.A., Nogueira M.G., Fearnside P.M., Lima L.B., Daga V.S., Oliveira F.J., Vitule J.R., Callisto M., Agostinho A.A., Esteves F.A., et. al.

Brazil has a variety of aquatic ecosystems and rich freshwater biodiversity, but these components have been constantly damaged by the expansion of unsustainable activities. An array of different conservation strategies is needed, especially the creation of protected areas (PAs, hereafter). However, Brazil's PAs are biased towards terrestrial ecosystems and we argue that current PAs have limited efficacy in the protection of freshwater biodiversity. New PAs should better consider aquatic environments, covering entire basins, rivers and other freshwater habitats. We recommend ways to implement these PAs and provide guidance to avoid social impacts. Freshwater systems in Brazil provide essential goods and services but these ecosystems are being rapidly degraded and will be lost if not adequately protected.

Rezende C.L., Scarano F.R., Assad E.D., Joly C.A., Metzger J.P., Strassburg B.B., Tabarelli M., Fonseca G.A., Mittermeier R.A.

New remote sensing data on vegetation cover and restoration opportunities bring hope to the Brazilian Atlantic Forest, one of the hottest of the 36 global biodiversity hotspots. Available estimates of remaining vegetation cover in the biome currently range from 11% to 16%. However, our new land-cover map, prepared at the highest resolution ever (5 m), reveals a current vegetation cover of 28%, or 32 million hectares (Mha) of native vegetation. Simultaneously, we found 7.2 Mha of degraded riparian areas, of which 5.2 Mha at least must be restored before 2038 by landowners for legislation compliance. Restoring the existing legal debt could increase native vegetation cover in the Atlantic Forest up to 35%. Such effort, if well planned and implemented, could reduce extinction processes by increasing connectivity of vegetation remnants and rising total native cover to above the critical biodiversity threshold established for different taxonomic groups. If undertaken, this process can be adaptive to climate change and boost sustainable development in this most populous biome in Brazil, turning it into a hopespot.

Luke S.H., Slade E.M., Gray C.L., Annammala K.V., Drewer J., Williamson J., Agama A.L., Ationg M., Mitchell S.L., Vairappan C.S., Struebig M.J.

There is a weak evidence base supporting the effective management of riparian ecosystems within tropical agriculture. Policies to protect riparian buffers—strips of non-cultivated land alongside waterways—are vague and vary greatly between countries. From a rapid evidence appraisal, we find that riparian buffers are beneficial to hydrology, water quality, biodiversity and some ecosystem functions in tropical landscapes. However, effects on connectivity, carbon storage and emissions reduction remain understudied. Riparian functions are mediated by buffer width and habitat quality, but explicit threshold recommendations are rare. Policy implications. A one-size fits all width criterion, commonly applied, will be insufficient to provide all riparian functions in all circumstances. Context-specific guidelines for allocating, restoring and managing riparian buffers are necessary to minimise continued degradation of biodiversity and ecosystem functioning in tropical agriculture.

Barlow J., França F., Gardner T.A., Hicks C.C., Lennox G.D., Berenguer E., Castello L., Economo E.P., Ferreira J., Guénard B., Gontijo Leal C., Isaac V., Lees A.C., Parr C.L., Wilson S.K., et. al.

The tropics contain the overwhelming majority of Earth’s biodiversity: their terrestrial, freshwater and marine ecosystems hold more than three-quarters of all species, including almost all shallow-water corals and over 90% of terrestrial birds. However, tropical ecosystems are also subject to pervasive and interacting stressors, such as deforestation, overfishing and climate change, and they are set within a socio-economic context that includes growing pressure from an increasingly globalized world, larger and more affluent tropical populations, and weak governance and response capacities. Concerted local, national and international actions are urgently required to prevent a collapse of tropical biodiversity. The immense biodiversity of tropical ecosystems is threatened by multiple interacting local and global stressors that can only be addressed by the concerted efforts of grassroots organizations, researchers, national governments and the international community.

Soga M., Gaston K.J.

MS was supported by the Japan Society for the Promotion of Science (grant no. 16K00631), and KJG by the Natural Environment Research Council (grant no. NE/J015237/1).

de Oliveira Roque F., Menezes J.F., Northfield T., Ochoa-Quintero J.M., Campbell M.J., Laurance W.F.

We evaluate potential warning signals that may aid in identifying the proximity of ecological communities to biodiversity thresholds from habitat loss—often termed “tipping points”—in tropical forests. We used datasets from studies of Neotropical mammal, frog, bird, and insect communities. Our findings provide only limited evidence that an increase in the variance (heteroskedasticity) of biodiversity-related parameters can provide a general warning signal of impending threshold changes in communities, as forest loss increases. However, such an apparent effect was evident for amphibians in the Brazilian Atlantic Forest and Amazonian mammal and bird communities, suggesting that impending changes in some species assemblages might be predictable. We consider the potential of such warning signs to help forecast drastic changes in biodiversity.

Brejão G.L., Hoeinghaus D.J., Pérez-Mayorga M.A., Ferraz S.F., Casatti L.

Deforestation is a primary driver of biodiversity change through habitat loss and fragmentation. Stream biodiversity may not respond to deforestation in a simple linear relationship. Rather, threshold responses to extent and timing of deforestation may occur. Identification of critical deforestation thresholds is needed for effective conservation and management. We tested for threshold responses of fish species and functional groups to degree of watershed and riparian zone deforestation and time since impact in 75 streams in the western Brazilian Amazon. We used remote sensing to assess deforestation from 1984 to 2011. Fish assemblages were sampled with seines and dip nets in a standardized manner. Fish species (n = 84) were classified into 20 functional groups based on ecomorphological traits associated with habitat use, feeding, and locomotion. Threshold responses were quantified using threshold indicator taxa analysis. Negative threshold responses to deforestation were common and consistently occurred at very low levels of deforestation (10 years after impact. Findings were similar at the community level for both taxonomic and functional analyses. Because most negative threshold responses occurred at low levels of deforestation and soon after impact, even minimal change is expected to negatively affect biodiversity. Delayed positive threshold responses to extreme deforestation by a few species do not offset the loss of sensitive taxa and likely contribute to biotic homogenization.

Freitas F.L., Englund O., Sparovek G., Berndes G., Guidotti V., Pinto L.F., Mörtberg U.

Brazil is one of the major contributors to land-use change emissions, mostly driven by agricultural expansion for food, feed, and bioenergy feedstock. Policies to avoid deforestation related to private commitments, economic incentives, and other support schemes are expected to improve the effectiveness of current command and control mechanisms increasingly. However, until recently, land tenure was unknown for much of the Brazilian territory, which has undermined the governance of native vegetation and challenged support and incentive mechanisms for avoiding deforestation. We assess the total extent of public governance mechanisms protecting aboveground carbon (AGC) stocks. We constructed a land tenure dataset for the entire nation and modeled the effects and uncertainties of major land-use acts on protecting AGC stocks. Roughly 70% of the AGC stock in Brazil is estimated to be under legal protection, and an additional 20% is expected to be protected after areas in the Amazon with currently undesignated land undergo a tenure regularization. About 30% of the AGC stock is on private land, of which roughly two-thirds are protected. The Cerrado, Amazon, and Caatinga biomes hold about 40%, 30%, and 20% of the unprotected AGC, respectively. Effective conservation of protected and unprotected carbon will depend on successful implementation of the Forest Act, and regularization of land tenure in the Amazon. Policy development that prioritizes unprotected AGC stocks is warranted to promote conservation of native vegetation beyond the legal requirements. However, different biomes and land tenure structures may require different policy settings considering local and regional specifics. Finally, the fate of current AGC stocks relies upon effective implementation of command and control mechanisms, considering that unprotected AGC in native vegetation on private land only accounts for 6.5% of the total AGC stock.

Leal C.G., Barlow J., Gardner T.A., Hughes R.M., Leitão R.P., Mac Nally R., Kaufmann P.R., Ferraz S.F., Zuanon J., de Paula F.R., Ferreira J., Thomson J.R., Lennox G.D., Dary E.P., Röpke C.P., et. al.

1. Agricultural expansion and intensification are major threats to tropical biodiversity. In addition to the direct removal of native vegetation, agricultural expansion often elicits other human-induced disturbances, many of which are poorly addressed by existing environmental legislation and conservation programmes. This is particularly true for tropical freshwater systems, where there is considerable uncertainty about whether a legislative focus on protecting riparian vegetation is sufficient to conserve stream fauna. 2. To assess the extent to which stream fish are being effectively conserved in agricultural landscapes, we examined the spatial distribution of assemblages in river basins to identify the relative importance of human impacts at instream, riparian and catchment scales, in shaping observed patterns. We used an extensive dataset on the ecological condition of 83 low-order streams distributed in three river basins in the eastern Brazilian Amazon. 3. We collected and identified 24,420 individual fish from 134 species. Multiplicative diversity partitioning revealed high levels of compositional dissimilarity (DS) among stream sites (DS = 0.74 to 0.83) and river basins (DS = 0.82), due mainly to turnover (77.8% to 81.8%) rather than nestedness. The highly heterogeneous fish faunas in small Amazonian streams underscore the vital importance of enacting measures to protect forests on private lands outside of public protected areas. 4. Instream habitat features explained more variability in fish assemblages (15%-19%) than riparian (2%-12%), catchment (4%-13%) or natural covariates (4%-11%). Although grouping species into functional guilds allowed us to explain up to 31% of their abundance (i.e. for nektonic herbivores), individual riparian - and catchment- scale predictor variables that are commonly a focus of environmental legislation explained very little of the observed variation (partial R-2 values mostly 5. Policy implications. Current rates of agricultural intensification and mechanization in tropical landscapes are unprecedented, yet the existing legislative frameworks focusing on protecting riparian vegetation seem insufficient to conserve stream environments and their fish assemblages. To safeguard the species-rich freshwater biota of small Amazonian streams, conservation actions must shift towards managing whole basins and drainage networks, as well as agricultural practices in already-cleared land.

Strassburg B.B., Brooks T., Feltran-Barbieri R., Iribarrem A., Crouzeilles R., Loyola R., Latawiec A.E., Oliveira Filho F.J., Scaramuzza C.A., Scarano F.R., Soares-Filho B., Balmford A.

Despite projections of a severe extinction event, a window of opportunity is now open for a mix of policies to avoid biodiversity collapse in the Cerrado hotspot.

van Nes E.H., Arani B.M., Staal A., van der Bolt B., Flores B.M., Bathiany S., Scheffer M.

Over the past 10 years the use of the term 'tipping point' in the scientific literature has exploded. It was originally used loosely as a metaphor for the phenomenon that, beyond a certain threshold, runaway change propels a system to a new state. Although several specific mathematical definitions have since been proposed, we argue that these are too narrow and that it is better to retain the original definition.

Dala-Corte R.B., Giam X., Olden J.D., Becker F.G., Guimarães T.D., Melo A.S.

Summary Understanding mechanisms by which agricultural practices affect freshwater ecosystems helps to inform land-use policies and management strategies aimed at mitigating effects of agriculture on biodiversity. Land-use activities in the catchment, riparian and local scales likely influence stream fish communities via multiple pathways, for instance, by modifying the instream habitat. We investigated the mechanisms driving local stream fish taxonomic richness and functional diversity in South Brazilian grasslands by testing a theoretical path model in which we specified a priori relationships predicting how land use at multiple scales affects instream habitat and fish communities. Agricultural activities adjacent to streams (i.e. local impact on the streambank) and catchment-scale cropland area were positively related to macrophyte cover and negatively associated with coarse particulate organic matter (CPOM, i.e. woody debris and leaf litter). Local impact also increased substrate siltation and homogenisation. Riparian vegetation in the upstream buffer ameliorated instream habitat condition by dampening macrophyte proliferation and providing CPOM. Fish species richness increased with both macrophyte cover and CPOM, revealing multiple pathways of agricultural influence. However, functional diversity decreased only with substrate siltation, revealing a response to agricultural activities adjacent to sample sites. Agricultural streams showed a replacement of benthic and lithophilic species by a larger number of morphologically similar and macrophyte-associated nektonic fish. Our study indicates that land-use adjacent to streams and upstream riparian zones is critical for maintaining taxonomically and functionally diverse fish communities due to their strong effects on instream habitat. Protection and recovery of riparian zones from land-use change can mitigate the effects of agriculture on fish communities in South Brazilian grasslands.

Leitão R.P., Zuanon J., Villéger S., Williams S.E., Baraloto C., Fortunel C., Mendonça F.P., Mouillot D.

There is broad consensus that the diversity of functional traits within species assemblages drives several ecological processes. It is also widely recognized that rare species are the first to become extinct following human-induced disturbances. Surprisingly, however, the functional importance of rare species is still poorly understood, particularly in tropical species-rich assemblages where the majority of species are rare, and the rate of species extinction can be high. Here, we investigated the consequences of local and regional extinctions on the functional structure of species assemblages. We used three extensive datasets (stream fish from the Brazilian Amazon, rainforest trees from French Guiana, and birds from the Australian Wet Tropics) and built an integrative measure of species rarity versus commonness, combining local abundance, geographical range, and habitat breadth. Using different scenarios of species loss, we found a disproportionate impact of rare species extinction for the three groups, with significant reductions in levels of functional richness, specialization, and originality of assemblages, which may severely undermine the integrity of ecological processes. The whole breadth of functional abilities within species assemblages, which is disproportionately supported by rare species, is certainly critical in maintaining ecosystems particularly under the ongoing rapid environmental transitions.

Sousa K.S., Brito J.S., Cruz G.M., Bastos R.C., Mendoza-Penagos C.C., Silva E., Montag L., Oliveira-Junior J.M., Brejão G., Casatti L., Michelan T.S., Juen L., Dias-Silva K.

Ferreira P.H., Lima E.L., Lima-Junior D.P., Brasil L.S.

Augusto F.G., Araújo M.G., Callisto M., Linares M.S., Martinelli L.A.

Human land uses modify energy flux and nutrient cycles between terrestrial and freshwater ecosystems. Because aquatic macroinvertebrates are key components in nutrient cycling and food webs, their isotopic compositions can provide clues about the energy and matter flows between riparian-aquatic ecosystems through their producer–consumer relationships. Therefore, our objective was to investigate how land use affects food assimilation by aquatic macroinvertebrates. We measured the δ13C and δ15N values of aquatic macroinvertebrates and potential food sources at 12 stream sites under different riparian land uses: secondary riparian forests and agricultural (pasture and sugarcane). We had two hypotheses: (1) the δ15N of aquatic macroinvertebrates would be higher in sites with more agricultural areas and (2) the overall contribution of C4 plants to aquatic macroinvertebrates would be low in all sites, but higher in sites with more agricultural areas. We found higher values of δ15N in sites with forested riparian zones than those with agricultural riparian zones, rejecting our first hypothesis. The disturbances in riparian zones are indicated in δ13C and δ15N aquatic macroinvertebrate signatures. The second hypothesis was partially supported: i.e., the C4 plants represented < 12% of aquatic macroinvertebrate diet composition, the lowest assimilation rates regardless of the riparian land use, but it was not necessarily higher at sites with more agricultural areas. Our results reinforce the greater importance of C3 plants and autochthonous material contribution to aquatic macroinvertebrate diets and the importance of protecting riparian vegetation, which plays a fundamental role in aquatic ecosystem functioning in tropical headwater streams.

Linares M.S., Macedo D.R., Marques J.C., Hughes R.M., Callisto M.

Graça M.A., Wantzen K.M., Teixeira de Mello F., Callisto M., Rodríguez-Olarte D.

Akinpelu O.T., Arimoro F.O., Ayanwale A.V., Chukwuemeka V.I., Adedapo A.M., Akindele E.O.

Riparian forest loss and various land use impacts on macroinvertebrate communities in Nigerian streams remain poorly understudied. To fill this knowledge gap, a study was conducted on five streams in the southwest ecoregion of Nigeria between December 2019 and October 2021. A total of 2,077 macroinvertebrates were sampled, comprising 16 orders, 40 families, and 80 species. Aquatic insects were the most abundant, constituting 85 % of species and 73.13 % of individuals. Other specimens included Mollusca, Crustacea, Arachnida, and Annelida. Notably, Olumirin stream exhibited the highest macroinvertebrate abundance, including the stress-sensitive Ephemeroptera-Plecoptera-Trichoptera (EPT) members. The site also had the highest degree of naturalness, widest channel and dissolved oxygen (DO), but lowest electrical conductivity (EC) and total dissolved solids (TDS) compared to the other streams (Abirunmu, Awoosun, Mogimogi, and Aboto), that harbored facultative and stress-tolerant species, indicating varying degrees of disturbances. The bivariate regression analysis confirms that riparian deforestation and land use impact macroinvertebrate distribution in streams as there was an inverse relationship between EPT abundance and forest cover. Also, DO positively correlates with EPT taxa richness but inversely correlates with Coleoptera richness and Hemiptera abundance. As a result, Olumirin stream is proposed as a benchmark for evaluating freshwater ecological integrity in the region. Given the escalating anthropogenic activities in the tropics, urgent collaborative efforts are required to safeguard freshwater biodiversity, protect the riparian corridor of Olumirin stream, and restore impaired streams in the region.

Martins R.T., Firmino V.C., Hamada N.

Multiple local anthropogenic pressures and climate changes threaten the biodiversity of aquatic insects in the Amazon. In this chapter, we review the impacts of various land use practices (e.g., urbanization, pasture, agriculture, mining, and dams) and climate change on aquatic insect assemblages in the Amazon region. We explore how these factors might influence the composition, richness, abundance, diversity, and ecosystem processes (e.g., leaf decomposition) of these insect communities. Finally, we outline future perspectives for studies of insects and aquatic environments in the Amazon.

Zingel P., Agasild H., Tuvikene A.

The Amazon rainforest’s aquatic food webs are facing unprecedented challenges due to climate and land-use change. A diverse array of organisms is supported by these intricate and interconnected ecosystems, but the increasing threat of droughts and deforestation is disrupting the delicate balance of life. The Amazon food webs derive their energy from two primary sources: an autochthonous source, dependent on the productivity of the aquatic ecosystem (such as phytoplankton and aquatic macrophytes), and an allochthonous source, mainly from seasonally flooded forests (comprising fallen fruits and seeds that enter the water). The Amazonian food webs are currently influenced by various factors, including climate change and flooding patterns. These factors impact the structure, function, and energy sources of the food webs, affecting the abundance and distribution of organisms such as phytoplankton, bacteria, macrophytes, and invertebrates. The flood pulses have a pivotal role in shaping these food webs, affecting nutrient availability and impacting the abundance and biomass of fish. The interactions between the terrestrial and aquatic components are vital for the operation of Amazonian food webs, where floodplains serve significant functions as both nursery and feeding areas for numerous fish species. The disruption of food chains in the Amazon as a result of climate and land-use change is exemplified by the drying of aquatic habitats and changes in the fish community of floodplain lakes. This event generates a new scenario that has significant consequences for the ecological balance and productivity of the region, highlighting the urgent need for conservation and protection efforts.

Fernando A.M., Severo‐Neto F., Ferreira F.S., Mateus L., Tondato‐Carvalho K.K., Kashiwaqui E.A., Gimenes Junior H., Domingues W.M., Pavanelli C.S., Pinho H.L., Penha J., Súarez Y.R.

AbstractLack of sufficient knowledge of biological diversity is the first barrier to promoting scientifically‐based conservation policies in Neotropical regions, where high diversity and limited sampling remains a challenge. We compiled fish occurrences data from the whole Upper Paraguay River basin (UPRB) and evaluated the altitudinal variation in species richness, local contribution to beta diversity (LCBD) and composition. We also evaluate the influence of other environmental variables on species richness. Occurrence of a total of 342 native and five exotic fish species were recorded. Fish species richness was higher in lower portions of the basin, with a clear decrease from 400 m.a.s.l. Richness was negatively correlated with altitude, and positively correlated with net primary productivity and slope. The LCBD presented higher values on floodplain and in headwaters. Intermediate classes presented greater relative importance, as they present greater relative richness in a small relative area in the basin. We observed a partial overlap in species composition along altitude classes. Three species classified in some category of threat according to the conservation status of ichthyofauna in Brazil have a limited spatial extent of occurrence, restricted within the Serra da Bodoquena plateau. The obtained results highlight the unique diversity in the floodplain–plateau continuum, therefore, choosing protected areas must consider altitude gradients in the UPRB. Given the small area of the conservation units in the basin, the important role of higher altitude streams in regional fish species diversity and the several threats in the plateau, we conclude that an increase in conservation effort is needed in the plateau portion of the Upper Paraguay River basin.

Moura L.P., Viana C.G., Juen L., Couceiro S.R.

The biological diversity of a region may not be fully sampled due to the low abundance or rarity of species, or the absence of species determined by their niche specificity. Investigating these species is essential for understanding the unrealized ecological potential in different habitats, identifying gaps in local and regional communities, and gaining a better understanding of the impacts of environmental changes. Therefore, to expand knowledge about the diversity of Odonata in Eastern Amazonia considering the absent species, we tested the hypotheses that: 1) Environmental variables will influence dark diversity, with greater explanation by canopy cover where sites with lower canopy cover will have higher dark diversity values, and; 2) Functional traits associated with better species dispersal will be correlated with low dark diversity of Odonata, such as larger and wider wings for example. For this, adult Odonata specimens were sampled, while structural habitat characteristics and physical and chemical water variables were measured in 128 first- to third-order streams in the Eastern Amazon. Morphological and behavioral data were recorded for each specimen. Generalized linear models were applied to predict the effects of habitat structural characteristics and physical and chemical water variables on the dark diversity of Odonata. Additionally, we assessed which functional traits contribute most to the variation of dark diversity within these communities. Habitat structural features and physical and chemical water variables had no effect on dark diversity. Morphological traits, such as body conformation, with species having narrower wings, longer hind wings, narrower thoraxes, and shorter abdomens, comprised most of the dark diversity. The dispersal limitations of some Odonata species strongly suggest the role of space and time in nature planning and management.

Thomaz S.M., Benassi S.F., Benassi R.F.

Abstract Water security involves ensuring that water is available in sufficient quality and quantity to meet the needs of human health, livelihoods, ecosystems, and productive activities. This opinion paper highlights the crucial role of Long-Term Ecological Research (LTER) in shaping strategies to achieve water security. We begin by defining both water security and LTER, and by illustrating how LTER contributes to securing water resources. We then briefly discuss the significance of early long-term studies that have laid the foundation for water security efforts. Following this, we examine LTER programs focused on freshwater ecosystems in Brazil, with particular emphasis on two case studies in the Upper Paraná River: the LTER program in the Upper Paraná River floodplain and the monitoring of macrophytes in the Itaipu Reservoir. We show that long-term studies in Brazil have supported the implementation of strategies that benefit various dimensions of water security, positively impacting supporting, provisioning, regulating, and cultural ecosystem services. Finally, we discuss the incorporation of water security into Brazilian legislation. While Brazilian scientists and managers possess experience in both LTER and water security issues, ensuring the implementation and enhancement of the benefits through legislative measures and other instruments that prioritize most of the society, rather than catering solely to the most influential economic sectors is challenging.

Campos C.A., Tonin A.M., Sena G., Gonçalves Júnior J.F.

Diverse anthropogenic activities have threatened the valuable tropical biodiversity and freshwater reserves. Despite that, there is little concern in the Brazilian legislation about the ecological integrity of aquatic ecosystems. We proposed a framework based on two joint indices, allowing the creation of a management tool. The first is the Tropical Water Healthy Index (TWHI), a river index that integrates pressures on aquatic ecosystems, their conditions, and societal/governmental response. The second is the Suitability of the Class of Use (SCU), which measures whether rivers’ conditions are in accordance with their classes of use proposed for the legal Brazilian water framework. Our results showed that most sites had good river health conditions, with the worst conditions occurring in areas with high urban occupations followed by agricultural areas. The second index indicated that few streams were poorly or incompatible with their classes of use, suggesting their classifications were based on current conditions but not future intentions. The force of these joint analyses was shown in the Melchior River stretch, which was classified as compatible with SCU, but the TWHI was critical. This is good to show that we simultaneously have a problem with the legislation and to indicate something that needs to be done quickly for managers. Therefore, we built a management model that can assess the real situation of aquatic ecosystems and define efficient management strategies, producing alerts for the decision-maker.

Tabi A., Santos E.P., Brejão G., Siqueira T.

AbstractLand use change affects the biodiversity of terrestrial landscapes as well as of the freshwater systems they surround, and thereby numerous ecosystem services that are essential for human well-being. Previous research suggests that freshwater systems show delayed responses to abrupt disturbances such as deforestation, however less is known about whether there is a legacy effect of landscape history on freshwater communities under a long history of land use change. We addressed this research gap here by first quantifying the historical complexity of landscapes, including natural and agricultural formations, in terms of their composition and configuration in 26 tropical catchment areas surrounding 101 streams over a 30-year period. We identified clear evidence for a memory effect of past events, whereby historical landscape complexity, measured as the information entropy of landscape composition, positively affected freshwater biodiversity. Finally, using a causal discovery approach, we showed that species richness was causally related to landscape complexity only when historical values were incorporated. Our results corroborate previous work on the positive effect of landscape complexity on biodiversity, and also confirm the role of historical contingencies in predicting future ecological outcomes.

Miñana-Albanell C., Ryu D., Pérez-Martín M.Á.

Water temperature is a critical factor for aquatic ecosystems, influencing both chemical and biological processes, such as fish growth and mortality; consequently, river and lake ecosystems are sensitive to climate change (CC). Currently proposed CC scenarios indicate that air temperature for the Mediterranean Jucar River will increase higher in summer, 4.7 °C (SSP5-8.5), resulting in a river water temperature increase in the hotter month; July, 2.8 °C (SSP5-8.5). This will have an impact on ecosystems, significantly reducing, fragmenting, or even eliminating natural cold-water species habitats, such as common trout. This study consists of developing a simulated model that relates the temperature of the river with the shadow generated by the riverside vegetation. The model input data are air temperature, solar radiation, and river depth. The model proposed only has one parameter, the shadow river percentage. The model was calibrated in a representative stretch of the Mediterranean river, obtaining a 0.93 Nash–Sutcliffe efficiency coefficient (NSE) that indicates a very good model fit, a 0.90 Kling–Gupta efficiency index (KGE), and a relative bias of 0.04. The model was also validated on two other stretches of the same river. The results show that each 10% increase in the number of shadows can reduce the river water temperature by 1.2 °C and, in the stretch applied, increasing shadows from the current status of 62% to 76–87% can compensate for the air temperature increase by CC. Generating shaded areas in river restorations will be one of the main measures to compensate for the rise in water temperature due to climate change.

Shen M., van Klink R., Sagouis A., Petsch D., Abong'o D., Alahuhta J., Al‐Shami S., Armendáriz L., Bae M., Begot T., Belliard J., Benstead J., Bomfim F., Bredenhand E., Budnick W., et. al.

ABSTRACTMotivationFreshwater ecosystems have been heavily impacted by land‐use changes, but data syntheses on these impacts are still limited. Here, we compiled a global database encompassing 241 studies with species abundance data (from multiple biological groups and geographic locations) across sites with different land‐use categories. This compilation will be useful for addressing questions regarding land‐use change and its impact on freshwater biodiversity.Main Types of Variables ContainedThe database includes metadata of each study, sites location, sample methods, sample time, land‐use category and abundance of each taxon.Spatial Location and GrainThe database contains data from across the globe, with 85% of the sites having well‐defined geographical coordinates.Major Taxa and Level of MeasurementThe database covers all major freshwater biological groups including algae, macrophytes, zooplankton, macroinvertebrates, fish and amphibians.