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Insights into the coexistence of birds and humans in cropland through meta-analyses of bird exclosure studies, crop loss mitigation experiments, and social surveys [1]

['Cheng Huang', 'State Key Laboratory Of Biological Control', 'Sun Yat-Sen University', 'Guangzhou', 'School Of Life Sciences', 'State Key Laboratory Of Genetic Resources', 'Evolution', 'Kunming Institute Of Zoology', 'Chinese Academy Of Science', 'Kunming']

Date: 2023-07

Birds share lands with humans at a substantial scale and affect crops. Yet, at a global scale, systematic evaluations of human–bird coexistence in croplands are scarce. Here, we compiled and used meta-analysis approaches to synthesize multiple global datasets of ecological and social dimensions to understand this complex coexistence system. Our result shows that birds usually increase woody, but not herbaceous, crop production, implying that crop loss mitigation efforts are critical for a better coexistence. We reveal that many nonlethal technical measures are more effective in reducing crop loss, e.g., using scaring devices and changing sow practices, than other available methods. Besides, we find that stakeholders from low-income countries are more likely to perceive the crop losses caused by birds and are less positive toward birds than those from high-income ones. Based on our evidence, we identified potential regional clusters, particularly in tropical areas, for implementing win-win coexistence strategies. Overall, we provide an evidence-based knowledge flow and solutions for stakeholders to integrate the conservation and management of birds in croplands.

Funding: This study was funded by the State Key Laboratory of Genetic Resources and Evolution (GREKF20-03 to CH), National High-level Talent Program of China (41180953 to TML), and the DFGP Project of Fauna of Guangdong-202115 from Science and Technology Planning Projects of Guangdong Province (2021B121210002 to YL). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Copyright: © 2023 Huang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Introduction

Agriculture development is vital for reducing poverty and hunger [1], yet many agricultural practices substantially threaten over a quarter (27%) of all assessed 134,000 species (https://www.iucnredlist.org/). To minimize such threats, governments around the world have legally protected over 15% of the Earth’s land from human-oriented development for wildlife (land-sparing scenario) [2–4]. Meanwhile, humans and wildlife often share lands in or at the edge of agricultural landscapes (land-sharing scenario), where both ecosystem services and disservices of wildlife occur to humans [5,6]. Ecosystems services are the benefits that people derive from ecosystems, such as food provisions, crop pest controls, and recreations [7–10]. In contrast, ecosystem disservices are harmful to humans, such as livestock depredation and crop damage to farmers [11–14]. In the land-sharing scenario, wildlife-friendly agriculture is widely encouraged for a better coexistence and includes two major strategies in production: (i) integrating the beneficial biological service and (ii) mitigating the harmful impacts from the disservice [15,16].

Birds, distributed across the globe, share lands with humans at a substantial scale and provide diverse provisions (e.g., meat and eggs) and cultural services (e.g., birdwatching and ecotourism) to humans [7,9]. Also, birds affect crops through direct (e.g., crop consumption) and indirect (e.g., pest control) processes [8,10,17]. Thus, birds were often treated as a key indicator taxon of agricultural sustainability in global biodiversity conservation framework (e.g., Convention on Biological Diversity). Most birds prey on invertebrates, including not only herbivore arthropods (e.g., moth larvae and stink bugs) that consume plants but also predatory arthropods (e.g., spiders and ants) that predate these pest herbivores [18,19]. Birds have been shown to suppress the herbivore arthropods in wild plants and several crops [17,20]. Furthermore, birds not only provide pollination services for many plants [21], they also directly caused losses to farmers by consuming crops including cereals and fruits [22–25]. To our knowledge, there is presently a limited number of studies synthesizing evidence to show that the indirect services actually cascade down to crop production (but see [20,26]).

In reality, recognizing a service or value from wildlife by humans is often a prerequisite for tolerating a disservice [27–29]. In a complex bird-arthropod-crop system, the indirect service from birds (e.g., pest control) may be “socially” concealed by the direct crop damage since farmers mainly care about what they can observe directly [30,31]. As a result, birds, which provide potential beneficial services to crops, are often either improperly or mistakenly eliminated by poisoning, shooting, and entangle netting, for example, approximately 20% of bird individuals caught in rice fields were nontarget bycatch in the central plains of Thailand [32–34]. Therefore, systematic evaluations of the perception and attitude of crop producers toward birds and the effectiveness of nonlethal mitigating measures (e.g., using scaring devices and changing farming practices) are essential for bird-friendly policy-making and local practices.

Here, we provide a synthesis of the extent of human–bird coexistence in croplands from the direct (seen) damage to ecological cascades to crops, the human perceptions on the biological processes, and possible solutions to address the observed disservice by birds (Fig 1a). Using standard review protocols [35], we collected and screened relevant literature (“Search rules” and Fig A in S1 Text) and compiled 4 complementary global datasets (S1–S4 Data). Then, we used standard meta-analysis approaches [36], when possible, to understand four fundamental aspects of the complex system: (i) what is the spatial extent of the potential direct (seen) disservice or crop damage by crop-consuming birds (Fig 1b); (ii) whether birds can provide a net benefit to crop productions by accounting the direct (e.g., consume crops) and indirect effects (mainly referring to pest control) of birds (Fig 1c); (iii) if disservice exists, which nonlethal mitigation measures are effective (Fig 1d); and (iv) what are the public general perception and attitude towards birds (Fig 1e). Based on our results, we proposed a strategy for a better coexistence and discussed where to take possible actions at a regional scale (Fig 1f). Our study provides scientific evidence for multiple stakeholders to better integrate key conservation strategies and bird management in croplands.

PPT PowerPoint slide

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TIFF original image Download: Fig 1. A methodological overview for synthesizing evidence of human–bird coexistence in croplands. (a) Key components of human–bird coexistence system in croplands. (b) To identify crop-consuming species, all diet-related descriptions in the Birds of the World were compiled. (c) To evaluate the net effect of birds on different crop productions, we analyzed data from exclosure experiments, of which the access of birds to crops was intentionally manipulated. (d) To offer potential solutions for reducing crop loss from birds, we analyzed data from mitigation experiments to evaluate the effectiveness of available measures. (e) To explore human perceptions and attitudes toward birds, we evaluated data from different social surveys. Based on the evidence from (b), (c), and (d), we attempted to identify the priority areas to take actions for encouraging the coexistence. Such areas are characterized by a higher proportion of crop that benefits from birds’ service and higher bird conservation value (f). https://doi.org/10.1371/journal.pbio.3002166.g001

A tenth of all bird species are known to consume crops Birds affect crops directly (e.g., consume crops) that can be deemed as a disservice by local farmers. To understand the spatial extent of the potential direct (seen) disservices, we identify crop-consuming species by evaluating all the diet-related descriptions in the Birds of the World (BoW, hereafter), which is a comprehensive and widely used document about bird life history at a global scale [37–40]. For each species, the BoW provided a specific “Diet and Foraging” section, including the specific crops consumed by birds. The BoW reported that approximately 10% of all bird species (1,057 of >10,000 species; Table A in S1 Text) consume crops (Table B in S1 Text). The major groups of birds reported to consume woody (564 species) and herbaceous (708 species) crops are generally similar (Fig B in S1 Text), including the parrots (Psittacidae), finches (Fringillidae), pigeon or dove (Columbidae), ducks or geese (Anatidae), and New World blackbirds (Icteridae). About 11% of these crop-consuming species are threatened (i.e., Critically Endangered, Endangered, and Vulnerable; Fig 2a), which is similar to the overall threatened status of birds (i.e., 12.9%). In general, the crop-consuming birds are widely distributed, with higher richness reported in Europe, North America, East Africa, India, and Southeast Asia than in other regions (Fig 2b). PPT PowerPoint slide

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TIFF original image Download: Fig 2. Number of bird species reported to consume crops and the overlay of their range distributions. The top barplot (a) shows the number of bird species reported to consume crops of taxonomic families by the IUCN threatened status (the data underlying this figure can be found in S1 Data). Only families with the top 25% number of species were plotted. The bottom map (b) shows the overlay of the range distribution maps of 1,057 crop-consuming bird species. The base map of country boundaries was from https://www.naturalearthdata.com/. https://doi.org/10.1371/journal.pbio.3002166.g002

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[1] Url: https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3002166

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