Bats respond negatively to increases in the amount and homogenization of agricultural land cover

Abstract from paper: Changes in agricultural landscapes due to intensification, such as loss of natural areas, loss of grazing lands to annual row crops, and increased use of pesticides, have led to widespread declines in biodiversity. Bats are expected to respond negatively to agricultural intensification because of reductions in prey abundance and roosting habitat availability. We measured relative bat abundance with acoustic bat recorders in landscapes that varied in (1) the proportion of agriculture and (2) the proportion of agriculture that is in annual row crops vs. perennial forages (pasture and hay). We predicted that relative bat abundance would be highest where (1) the proportion of agriculture was low and (2) the agriculture was dominated by perennial forage. Consistent with our first prediction, the abundance or presence of four bat species, total bat abundance and bat species richness declined with increasing agricultural cover. Counter to our second prediction, we did not find a negative relationship between species richness or relative bat abundance or presence and the proportion of agricultural land that is in annual row crops. Instead we found that the abundance of three bat species, total bat abundance and bat species richness were greatest where the proportion of agriculture in annual crops was about equal to the proportion in perennial forage. Based on these results, we suggest that bat abundance and richness can be increased in agricultural landscapes by reducing the conversion of natural areas to agriculture and by maintaining a balance of perennial forage and annual crop agricultural cover types.

论文摘要：农业景观集约化引发的一系列变化，诸如自然生境丧失、一年生大田作物取代放牧地、农药使用量增加等，已造成生物多样性的大范围下降。由于猎物丰度降低以及栖息生境可获取性下降，蝙蝠通常会对农业集约化产生负面响应。我们利用声学蝙蝠记录仪，在两类存在差异的景观中测定了蝙蝠相对丰度：一类是农业用地占比不同的景观，另一类是农业用地中一年生大田作物与多年生饲草（牧场与干草田）占比不同的景观。我们此前预测，蝙蝠相对丰度最高的场景将满足两个条件：一是农业用地占比较低，二是农业用地以多年生饲草为主。与第一项预测相符的是，四种蝙蝠的丰度或出现率、蝙蝠总丰度以及蝙蝠物种丰富度均随农业覆盖度的升高而下降。然而与第二项预测相悖的是，我们并未发现物种丰富度、蝙蝠相对丰度或出现率与农业用地中一年生大田作物占比之间存在负相关关系。反而发现，当农业用地中一年生作物占比与多年生饲草占比大致相等时，三种蝙蝠的丰度、蝙蝠总丰度以及蝙蝠物种丰富度均达到最高水平。基于上述研究结果，我们提出：在农业景观中，可通过减少自然生境向农业用地的转化，以及维持多年生饲草与一年生大田作物两类农业覆盖类型的占比平衡，来提升蝙蝠的丰度与物种丰富度。