How many broadleaved trees are enough in conifer plantations? The economy of land sharing, land sparing and quantitative targets

Abstract

For biodiversity conservation to be an effective and significant social investment, non-marketed values of biodiversity conservation and its associated opportunity costs should be evaluated in monetary terms. In this study, we measured the willingness to pay (WTP) for bird abundance using a choice experiment (CE) based on the random utility model. We performed a cost-benefit analysis to identify the optimal proportion of broadleaved trees in conifer plantations on a volume basis to maximize the social benefits of bird conservation and wood production. The results suggested that respondents to the CE were not satisfied with their current situation and preferred an increase in bird abundance. However, the estimated WTP indicated diminishing returns of bird conservation. More specifically, WTP first greatly increased before gradually experiencing decreasing marginal values, reaching its peak and finally decreasing slightly with increasing bird abundance. Optimization analyses indicated that when the relationship between bird abundance and broadleaved tree proportion was convex, semi-natural plantations with nonzero broadleaved tree proportion (002-022) were always optimal options. When the relationship was linear, optimal broadleaved tree proportion ranged from 0 to 078 and was greatly affected by wood values. When the relationship was concave, there were only two optimal broadleaved tree proportions: a very high proportion (approximately 090) and the lowest possible proportion (0). When the convex and concave relationships approached the linear form, comparable benefits could be attained across broad ranges of broadleaved tree proportion both within and across the relationships. In such cases, it would be useful to increase the likelihood of a feasible land-use strategy of either land sparing or land sharing in order to be successful.Synthesis and applications. It can be difficult to set quantitative targets in biodiversity conservation solely on an ecological basis, and social benefits of biodiversity conservation can create diminishing returns in many situations. The framework we propose shows how to reconcile resource production and biodiversity conservation in the real world

Sharing land via keystone structure: Retaining naturally regenerated trees may efficiently benefit birds in plantations

“…Since the lowest amount of broad‐leaved trees in plantations before the harvest was 0.8 m 2 /ha rather than 0, we assumed that plantations naturally attain this amount of broad‐leaved trees with stand age (see also Lindbladh et al, 2022). We graphically represented the time‐averaged abundance against stumpage value, assuming that pure plantations had 300 m 3 /ha volumes of coniferous trees (Yamaura, Shoji, et al, 2016), which linearly decreased to 0 m 3 /ha when the forest comprised the maximum basal area of broad‐leaved trees (50 m 2 /ha). The stumpage price of coniferous trees was 1000 Japanese yen (JPY)/m 3 (Yamaura, Shoji, et al, 2016), and we did not account for the price of broad‐leaved trees, which were treated as nature reserves within plantations.…”

Concentrating vs. spreading our footprint: how to meet humanity's needs at least cost to nature

“…Among those studies that do include direct measures of biodiversity, several are limited by surveying just a few species, pooling abundance values across species, or not reporting yield (Calkin et al ., 2002; Yoshii et al ., 2015; Yamaura et al ., 2016; Mestre et al ., 2020). Of the analyses that quantify the abundance of large numbers of species across a wide yield spectrum, two studies – on 53 dung beetle species in Pará, Brazil (França et al ., 2017) and on 176 birds, 56 dung beetles and 214 ants in Borneo (Edwards et al ., 2014) – both suggest simple two‐compartment sparing would outperform sharing.…”

Producing wood at least cost to biodiversity: integrating Triad and sharing–sparing approaches to inform forest landscape management

“…However, the few theoretical (Seymour & Hunter, 1992) and modelling (Tittler, Messier & Fall, 2012; Tittler et al ., 2015) studies aimed at determining optimal proportions of different management regimes in the Triad approach (Ward & Erdle, 2015; Tittler et al ., 2016) are limited in value due to the absence of sufficient empirical data to identify formally how best to minimize impacts to biodiversity while meeting any given level of demand for wood (Messier et al ., 2009; Yoshii et al ., 2015; Yamaura et al ., 2016; but see Section II). There are still few empirical tests of how differing landscape‐level proportions of land under the three Triad compartments alters species’ populations and wood yield (Lindenmayer et al ., 2012) across entire landscapes.…”