Dryland Biodiversity Research Articles

Automatedly identify dryland threatened species at large scale by using deep learning

Dryland biodiversity is decreasing at an alarming rate. Advanced intelligent tools are urgently needed to rapidly, automatedly, and precisely detect dryland threatened species on a large scale for biological conservation. Here, we explored the performance of three deep convolutional neural networks (Deeplabv3+, Unet, and Pspnet models) on the intelligent recognition of rare species based on high-resolution (0.3 m) satellite images taken by an unmanned aerial vehicle (UAV). We focused on a threatened species, Populus euphratica, in the Tarim River Basin (China), where there has been a severe population decline in the 1970s and restoration has been carried out since 2000. The testing results showed that Unet outperforms Deeplabv3+ and Pspnet when the training samples are lower, while Deeplabv3+ performs best as the dataset increases. Overall, when training samples are 80, Deeplabv3+ had the best overall performance for Populus euphratica identification, with mean pixel accuracy (MPA) between 87.31 % and 90.2 %, which, on average is 3.74 % and 11.29 % higher than Unet and Pspnet, respectively. Deeplabv3+ can accurately detect the boundaries of Populus euphratica even in areas of dense vegetation, with lower identification uncertainty for each pixel than other models. This study developed a UAV imagery-based identification framework using deep learning with high resolution in large-scale regions. This approach can accurately capture the variation in dryland threatened species, especially those in inaccessible areas, thereby fostering rapid and efficient conservation actions.

Tracking endolithic microbiomes to support the sustainability and functioning of global drylands

AbstractDrylands cover almost half of the planet and support >25% the global population. In this era of global warming, they are expected to continue expanding by the end of the century as a consequence of predicted increases in aridity, which will affect multiple global locations that are already characterised by extreme temperatures, low and variable rainfall, and low soil fertility. In these fragile ecosystems, where microorganisms are integral to maintain functioning and primary productivity, endoliths (i.e., rock‐inhabiting microorganisms) play a key role in soil formation and dynamics and are and critical drivers of ecological succession. Here, we posit that endolithic microbes could also function as early alarm warning indicators for environmental changes in the most arid ecosystems. Nevertheless, studies on endoliths are still rather fragmentary and mainly focused in a few specific dry areas such as the Antarctic or Atacama deserts. A global appraisal of the structure and function of the endolithic microbiome is needed for the assessment of the current state of dryland biodiversity worldwide, and to identify the regions that are more vulnerable to global changes. Such an effort will provide new knowledge and will implement official and international initiatives to track and conserve biodiversity on global drylands.

The Overlooked Genetic Diversity in the Dryland Soil Surface-Dwelling Cyanobacterium Nostoc flagelliforme as Revealed by the Marker Gene wspA.

Biodiversity is recognized to be relatively low in the dryland ecosystem. However, we might overlook the accumulating genetic variation in those dryland micro-populations, which should eventually increase the dryland biodiversity. In the xeric steppes of western and northwestern China, there are two soil surface-dwelling and genetically close cyanobacterial species, Nostoc commune and Nostoc flagelliforme. They respectively exhibit lamellate and filamentous colony shapes. Their individual colony is consisted of hundreds of trichomes and the common exopolysaccharide matrix.N. flagelliforme is exclusively distributed in the dryland and supposed to be evolved from N. commune. We previously reported that the morphological diversity of N. flagelliforme colonies was very limited, being either cylindrical or strip-like. In this communication, we performed single-nucleotide polymorphism (SNP) analysis of the marker gene wspA as well as phylogenetic analysis of the WspA protein in N. flagelliforme colonies to gain insights into its genetic diversity. SNP analysis suggested that there existed plentiful nucleotide variations in the individual colonies and meanwhile these variations shared certain evolutionary regularity. Phylogenetic analysis of the deduced proteins from the cloned wspA sequences suggested that the relatively regular variations were possibly dispersed in the N. flagelliforme populations of different regions. Thus, these results presented a scenario of the underestimated genetic diversity hidden behind the limited morphotype of dryland cyanobacteria. Maybe, we can consider the individual cyanobacterial colony as a potential biodiversity pool in the drylands.

Impact of sheep grazing intensity on vegetation at the Arid Karoo Stocking Rate Trial after 27 years, Carnarvon, South Africa

Sustained heavy grazing is expected to result in degradation and loss of biodiversity in drylands but long-term experiments which assess the impact of management practises on biodiversity are necessary. The effects of stocking rate (SR) on vegetation composition, abundance of different plant functional groups (PFGs), abundance of dominant species, and plant diversity were investigated after 27 years at a long-term SR trial. Vegetation composition was investigated using Canonical Correspondence Analysis and General Linear Models. Stocking rate and time had significant effects on species composition. Increases over time were apparent for total plant cover, palatable shrub cover, and perennial grass cover, annual grass cover decreased over time, whereas other PFGs and rangeland condition showed no trend over time. Greater stocking rates resulted in lower total plant cover, palatable and unpalatable shrub cover, perennial grasses, and annual herbaceous species. Higher annual rainfall resulted in higher total plant cover, while greater preceding three-month rainfall benefitted annual grasses and annual herbaceous species. Plant diversity seemed unaffected by SR. Vegetation structure did not seem to be influenced by SR after 27 years. Our study confirms the slow rate at which vegetation change occurs in drylands and highlights the importance of long-term monitoring trials.

Impacts of future climate and land cover changes on threatened mammals in the semi-arid Chinese Altai Mountains

Dryland biodiversity plays important roles in the fight against desertification and poverty, but is highly vulnerable to the impacts of environmental change. However, little research has been conducted on dual pressure from climate and land cover changes on biodiversity in arid and semi-arid environments. Concequntly, it is crutial to understand the potential impacts of future climate and land cover changes on dryland biodiversity. Here, using the Chinese Altai Mountains as a case study area, we predicted the future spatial distributions and local assemblages of nine threatened mammal species under projected climate and land cover change scenarios for the period 2010–2050. The results show that remarkable declines in mammal species richness as well as high rates of species turnover are seen to occur across large areas in the Chinese Altai Mountains, highlighting an urgent need for developing protection strategies for areas outside of current nature reserve network. The selected mammals are predicted to lose more than 50% of their current ranges on average, which is much higher than species' range gains (around 15%) under future climate and land cover changes. Most of the species are predicted to contract their ranges while moving eastwards and to higher altitudes, raising the need for establishing cross-border migration pathways for species. Furthermore, the inclusion of land cover changes had notable effects on projected range shifts of individual species under climate changes, demonstrating that land cover changes should be incorporated into the assessment of future climate impacts to facilitate biodiversity conservation in arid and semi-arid environments.

Conserving dryland biodiversity: a future vision of sustainable dryland development

Water scarcity has largely driven the adaptations of organisms to survive dryland conditions. As a result, there are many animal and plant species and habitats found only in drylands: some semi-arid and dry sub-humid areas are among the most biodiverse regions in the world. Despite the value of such biomes, protected areas in drylands are not representative of all the dryland subtypes. For example, deserts are disproportionately represented whilst temperate grasslands have amongst the lowest level of protection of all biomes at approximately 3.4%. Nevertheless, local communities inhabiting drylands have informally conserved large areas as a by-product of sustainable management practices or cultural beliefs. The drylands offer significant opportunities for achieving both conservation and development objectives simultaneously and in many cases have been shown to do so. The Aichi targets (targets established by Parties to the Convention on Biological Diversity at the tenth Conference of Parties in 2010) on protected areas could be more easily achieved, or even surpassed, in drylands by legitimising and supporting Indigenous and Community Conserved Areas (ICCAs), and traditional natural resource management strategies. A more nuanced vision of sustainably managed drylands is therefore needed: one that reflects social and ecological realities and provides a framework against which policies and investments can be assessed. Such a vision should be based on the intersection between sustainable land management and biodiversity conservation, which encompasses the following four components: adapting green economic growth to the drylands; conservation and sustainable management of dryland biodiversity; and health as the basis for secure food and water provision; and resilience and risk management in uncertain environments. To realise such an ambitious vision in the drylands requires a strategic and broad suite of actions in the following four fields: innovation, knowledge and science; incentives and investment; governance and empowerment; mainstreaming dryland biodiversity.

Wetlands help maintain wetland and dryland biodiversity in the Sahel, but that role is under threat: an example from 80 years of changes at Lake Tabalak in Niger

Wetlands in arid and semi-arid regions are enormously important for the biodiversity of the surrounding drylands, and for the humans living there. Increasing human populations put increasing pressure on the dryland resources as well as on those wetlands. This case study of Lake Tabalak in Niger shows the changes that have taken place there over 80 years. From a tree-covered depression with a traditional well, it changed to a 1.150 ha lake in the 1970s. From this lake, where pastoralists and their livestock had free access to water and fodder all year round, it developed into a depression with almost wall-to-wall market gardens. In April–June, the end of the dry season, herders now have to pay large sums to have their animals feed on what there is of crop residues at the lake, before continuing to the natural grasslands further north once the rains have arrived. What little is left of the teeming wildlife in that region around 1940 is not coming to the lake anymore. The lake’s usefulness for trans-Saharan migratory birds has demonstrably decreased over the past 20 years. This lake, a key component in the dryland system it belongs to, facilitating year-round use of the drylands that surround it and connecting dry season grazing areas in the south to rainy season grasslands in the north, has become, or is becoming, degraded for all uses, not least wetland and dryland biodiversity. Increasing pressures over the coming decades will cause similar dryland systems elsewhere to suffer the same fate and lose important parts of their functionality and their biodiversity, if adequate countermeasures are not taken. Such countermeasures must concern the wetland systems rather than the individual wetlands that the dryland systems contain, and lead to participative integrated natural resource management involving all stakeholders, for instance through multi-stakeholder fora.

Antimycobacterial agents from selected Mexican medicinal plants

As part of the ICBG program Bioactive Agents from Dryland Biodiversity of Latin America, the present investigation was undertaken to explore the possible antimycobacterial potential of compounds derived from selected Mexican medicinal plants. Bioassay-guided fractionation of the crude extracts of Rumex hymenosepalus (Polygonaceae), Larrea divaricata (Zygophyllaceae), Phoradendron robinsonii (Loranthaceae) and Amphipteryngium adstringens (Julianiaceae) led to the isolation of several antimycobacterial compounds. Four stilbenoids, two flavan-3-ols and three anthraquinones were isolated from R. hymenosepalus. Two flavonols and nordihydroguaiaretic acid were obtained from L. divaricata. Sakuranetin was the antimycobacterial agent isolated from P. robinsonii. Two known triterpenoids and the novel natural product 3-dodecyl-1,8-dihydroxy-2-naphthoic acid were obtained from A. adstringens. In general, the isolates were identified by spectral means. The antimycobacterial activity of the secondary compounds isolated from the analysed species, as well as that of nine pure compounds previously isolated in our laboratories, was investigated; the MIC values ranged from 16 to 128 microg mL-1. Among the tested compounds, the glycolipids, sesquiterpenoids and triterpenoids showed the best antimycobacterial activity. The antimycobacterial property of the glycolipids is reported for the first time. Although the tested compounds showed moderate antimycobacterial activity, their presence in the analysed species provides the rationale for their traditional use in the treatment of tuberculosis.

The multidimensional nature of biodiversity and social dynamics and implications for contemporary rural livelihoods in remote Kalahari settlements, Botswana

AbstractDespite rapid socio‐economic development in Kalahari drylands, contemporary research suggests that biodiversity remains important as a component of the complex portfolio of livelihood strategies, as a real and perceived safety net in times of stress, and a key factor of cultural identity. The degree to which the spatially and temporally dynamic nature of biodiversity in drylands influences livelihoods is, however, little studied, particularly in socially complex contemporary rural settlements. Greater understanding in this area is required to allow better‐informed design and implementation of rural development, poverty alleviation and conservation initiatives. This is particularly true in the light of predicted increases in environmental dynamism with climate change. An interdisciplinary approach was used in two environmentally and socially distinct dryland settlements in Botswana, to investigate the extent to which the dynamic biodiverse setting influences contemporary rural livelihoods. Results illustrate that biodiversity, particularly its dynamics, is of critical contemporary importance to rural settlement livelihoods, particularly in times of inner settlement scarcity. Entitlements to biodiversity dynamics were, however, bound up by complex settlement‐specific social, economic and political factors. Unless such contextual within‐settlement dynamics are understood, the relative importance of biodiversity in rural development and poverty alleviation strategies in contemporary Kalahari drylands may be undermined.

10th Anniversary Review: Addressing land degradation and climate change in dryland agroecosystems through sustainable land management

Sustainable land management (SLM) is proposed as a unifying theme for current global efforts on combating desertification, climate change and loss of biodiversity in drylands. A focus on SLM will achieve the multiple goals of the three UN Conventions (UNCCD, UNFCCC and UNCBD) and in particular will address the roots causes of poverty and vulnerability to climate change rather than a current focus on adapting to climate change. The interlinkages between land degradation, climate change and loss of biodiversity are outlined together with a proposed set of interventions to achieve multiple goals. It is argued that improved land productivity is a viable goal to reduce poverty in drylands provided it is linked to payments for environmental services and better crop and weather insurances and coupled with alternative livelihoods that are not primarily dependent on land productivity. Obstacles to the achievement of SLM are discussed and the steps necessary to overcome them are presented. It is suggested that promoting SLM would be a better focus for the UNCCD than combating desertification.

Policy and education reform needs for conservation of dryland biodiversity

Increasing attention is devoted at the national, regional and international levels to in-situ conservation as a dynamic form of preservation of biodiversity and related local knowledge. The significance of drylands biodiversity for agricultural production, other human needs, and environmental protection is emphasised with particular reference to the Central and West Asia and North Africa (CWANA) region. The detrimental activities and processes leading to the rapid erosion of aridland biodiversity and, finally, to desertification on a large-scale are identified and discussed in relation to human population growth, urbanisation and poverty. Examples of regional projects on plant biodiversity conservation, ecosystem rehabilitation and sustainable utilization, which are carried out by the International Centre for Agricultural Research in the Dry Areas (ICARDA) with its National Agriculture Research Systems (NARS) partners in the region, are mentioned, and the contribution of farmers and herder communities through participation in these efforts is highlighted. A broad public awareness and education campaign at all levels, starting with the community members and school children and addressing other stakeholders, particularly national decision- and policy-makers and donor organisations, is essential for arresting and, hopefully, reversing the negative trends in the dryland's biodiversity degradation.