A bird's eye view of farm size and biodiversity: The ecological legacy of the iron curtain

Abstract

Agriculture is a major threat to global biodiversity. A common claim is that large-scale agro-industrial farming is mainly responsible for the biodiversity decline, while smaller family farms are more wildlife friendly. Here we leverage a natural experiment along the former inner German border to estimate the causal impact of farm size on biodiversity. We combine land cover data with bird diversity data to establish the mechanisms through which farm size affects bird diversity. Our main results show that the increase in farm size at the former inner German border reduces bird diversity by 15%. The results suggest further that the decline is the result of land cover simplification rather than land use intensification.

Preserving local biodiversity through crop diversification

“…The results of using these to estimate the same specification as the second column in Table 4, that is, including our full set of controls including the two pesticide proxies and the critical habitat control that do not reduce our sample size, are shown in the first column of Table 5. Accordingly, crop diversity measured non‐genetically has no significant impact on non‐genetic diversity of birds, as was also found by Redlich et al (2018) and Noack et al (2021), but in contrast to Hendershot et al (2020). In terms of the other land sharing‐sparing control variables, only the interaction term of GPP with the food crop share has a discernable impact, where the positive coefficient, as for phylogenetic diversity, indicates that for a given level food crop presence greater yield will increase bird richness.…”

“…Related to this, one should note that in the current literature specifically focusing on crop heterogeneity almost all current studies have been limited to cross‐sectional analysis, with the inclusion of a limited number of possibly confounding variables, usually just other landscape feature controls, in their regression analysis (Gottschalk et al, 2010; Hendershot et al, 2020; Lee & Goodale, 2018; Martin et al, 2020; Redlich et al, 2018; Wilson et al, 2017). Of the three studies that used panel data, Hendershot et al (2020) only examined differences in trends, whereas Frishkoff et al (2014) or Noack et al (2021) in their regression analysis ran a pooled cross‐section without accounting for location specific effects and using few controls. However, as noted by (Redlich et al, 2018), there are likely to be a number of possibly confounding factors other than landscape features that will determine both birds and cropland choices, such as geography, agricultural management practices, and climate, to name a few.…”

“…It also has been shown to be a good predictor of predictor of local ecosystems' functions and stability (Cadotte et al, 2009; Cadotte et al, 2012; Srivastava et al, 2012). However, of the existing literature cited above only Frishkoff et al (2014) calculated PD to capture avian diversity, whereas all others used the number of species (Hendershot et al, 2020; Redlich et al, 2018; Wilson et al, 2017), diversity indices based on the number of species (Frei et al, 2018; Noack et al, 2021), or the incidence of species (Lee & Goodale, 2018). Moreover, no current study has also simultaneously used a phylogenetic measure for crop hetereogeneity to capture its potential role in determining avian diversity.…”

Gridded 5 arcmin datasets for simultaneously farm-size-specific and crop-specific harvested areas in 56 countries

“…Whether smaller farms also generate higher yields has long been debated, although it appears that yields often correlate positively with farm size (see Rudra, 1968;Savastano and Scandizzo, 2017;Gollin, 2019;Ricciardi et al, 2021). What seems undisputed, however, is that smaller farms on average display greater biodiversity than their larger counterparts (Ricciardi et al, 2021;Noack et al, 2021).…”

Biodiversity-food trade-offs when agricultural land is spared from production

“…More rigorous empirical studies, on the other hand, tend to focus more on identifying the land-use and economic impacts of AES, for example, [27,28,29], neglecting biodiversity outcomes. While not focused on evaluating the impacts of AES, recent research using bird data has applied econometric methods to the evaluation of relationships between bird diversity and, respectively, insecticides [30], crop diversity [31], and farm size [32].…”