Abstract:

Climate changes has been shown to be related to the changes in the distributions of migratory species, which irreparably harms biodiversity. In this study, we evaluated the habitat change and population centroid shift for 7 orders and 23 different species on the IUCN (International Union for the Conservation of Nature and Natural Resources) Red List of migratory birds from 2014-2017 in current to mid-21st (2041-2700) century by Maximum Entropy method (MaxEnt) model. We found striking spatial variation in the suitability in geography, with Yangtze River basin losing 9.74% of suitable habitat and Pearl River basin losing 13% of habitat. The area of suitable habitat decreases over 3% of total habitat area in China under the RCP2.6, and decreases about 10% of total habitat area in China under RCP8.5 scenario, with the population centroid of habitat moving about 50 km to northeast on average. Furthermore, the suitability of migratory birds will decrease over 3% in future, which will be difficult for migratory birds to survive. The direction and distance of population centroid are different for every species. Most of the individual species in the study will move over 50 km and all the species will move towards to places with higher suitability. For the whole of China, the constraint for migratory birds is \(t_{\min}\). The dominant variable in southeast China is NDVI, and the northern China is altitude (alt). The decline in suitable habitat area and shift in population centroid will lead to the changes in the time and distance of migration process, resulting in more adverse conditions for the survival of migratory birds. Our study proves the adverse role of climate change in species distribution which is a prerequisite for protecting species in future.

Introduction

The number of migratory birds has declined dramatically worldwide since 1970 (Ims et al., 2019; Spooner et al., 2018). Key driver of the abundance decline is that climate change exacerbates the survival pressure of migratory birds (Jacome et al., 2019; Jetz et al., 2007; Lehikoinen et al., 2019; Mammola et al., 2018; Pearson et al., 2013; Russell et al., 2015; Saino et al., 2011; Spooner et al., 2018; Wilson et al., 2019; Yalcin & Leroux, 2018; Yu et al., 2019),which will result in the ecological imbalance and the absence of ecological function (Cohen et al., 2018; Hewson et al., 2016; Keogan et al., 2018). It is critical to understand how species spatial distribution changes under the changing climate for protecting biodiversity and formulating the effective policies (Northrup et al., 2019; Vickery et al., 2014).
In past decades, bird populations have declined and habitat has changed a lot. Roberts et al.(2019) assessed the change of avian spatial regimes and population in 46 years but did not explain the reason (Roberts et al., 2019). Previous studies have made great progress in studying the correlation between habitat distribution and climate change. Brawn et al.(2017)illustrated that the population of tropical birds was closely correlated to the climate in rainfall (Brawn et al., 2017). Climate change damages the region’s suitable environmental conditions for certain species (Sanchez-Bayo & Wyckhuys, 2019; Title & Bemmels, 2018),which leads to change in their geographic range (Keogan et al., 2018; Saino et al., 2011). Climate change makes that the growth cycle of migratory birds hardly keep the match between the feeding time and the period of rich food resources (Bowler et al., 2019; Fecchio et al., 2019; Jetz et al., 2007; Kentie et al., 2018; Wilson et al., 2019). Bowler et al.(2019) corroborated the general trend that European insectivorous birds communities was confirmed to be the same as insect (Bowler et al., 2019). Saino et al.(2011) confirmed the reason of the population decline of European migratory birds was that their migration phenology mismatches the climate (Saino et al., 2011). Despite these lines of evidence, little research has been done to identify the effects of individual climate variables on species distribution. Better identification of major climate variables can help to establish effective policies, which is one of the urgent needs for biodiversity conservation (Beringer et al., 2011; Both et al., 2010; Cohen et al., 2018; Dugger et al., 2016; Hoffmann & Sgro, 2011).
Theoretical research on the correlation between species distribution and climate change is meaningful to protect biodiversity. To understand the effect of climate change on the potential distribution pattern of species, research model has become an important means. Saupe et al.(2019) demonstrated the MaxEnt model performed well for evaluating the changes in the distribution of birds at the geographical level (Saupe et al., 2019). The presence data is widely used in the species distribution model combing with climate data and proved to be feasible (Finch et al., 2017; Jacome et al., 2019; Roberts et al., 2019; Saupe et al., 2019).
In this study, we combined bird sample data and China national scale climate data to build the species distribution models(SDMs) for 7orders of migratory birds and 23species in different level on the IUCN red list (Moran & Kanemoto, 2017). In the study , we explored the current distribution and the drivers by MaxEnt, and discussed where and how the distribution may change in the 2050s. Firstly, we used the model to simulate the current distribution of migratory birds and predicted their distribution under the future scenarios. Secondly, based on the simulation of birds’ distribution, we quantified the movement trend by calculating the species population centroid and identified the individual contribution of environmental variables. Lastly, we compared the differences between the distribution and the protected areas to discuss the effective methods for reducing the biodiversity loss.
  1. Material and methods

    Species data

Migratory birds transport the energy and nutrients within and between the ecosystems, which is the largest population movement in the world, connecting the world into a huge ecosystem (Bauer & Hoye, 2014; Russell et al., 2015). The population of migratory birds passing through the major flyways dropped by half over the past 30 years (Runge et al., 2015) and migratory birds got into an unfavorable position in Asia (Kirby et al., 2008).
China is the largest country in Asia lying in East Asian-Australasian flyways with high biodiversity (Ma et al., 2019).We compiled migratory bird data from 2014–2017 Bird Report(http://www.birdreport.cn/). The Bird Report is the most complete and effective summary by bird watchers in China, accounting for 80% of all bird species, and each birdwatching record is sorted up and reviewed by experts to ensure accuracy. The latitude and longitude of the location were determined by comparing the geographical locations in Google Earth. We recorded the bird presence data in ArcGIS10.2, and selected 7 orders of migratory birds, including 115 species, covering 12156 geographical records. 23 species are endangered species on the IUCN red list(Fig1) (Garnett et al., 2003; Young et al., 2014). After deleting the duplicate invalid data, we modelled the potential distribution of both 7 orders of migratory birds and 23 different IUCN categories species, including 3 critically endangered (CR) species, 5 endangered (EN) species, 9 vulnerable(VU) species and 6 near threatened(NR) species(Table S1). The locations of migratory birds is showed in Fig.1.