Land use intensification alters ecosystem multifunctionality via loss of biodiversity and changes to functional composition

Abstract

Global change, especially land-use intensification, affects human well-being by impacting the delivery of multiple ecosystem services (multifunctionality). However, whether biodiversity loss is a major component of global change effects on multifunctionality in real-world ecosystems, as in experimental ones, remains unclear. Therefore, we assessed biodiversity, functional composition and 14 ecosystem services on 150 agricultural grasslands differing in land-use intensity. We also introduce five multifunctionality measures in which ecosystem services were weighted according to realistic land-use objectives. We found that indirect land-use effects, i.e. those mediated by biodiversity loss and by changes to functional composition, were as strong as direct effects on average. Their strength varied with land-use objectives and regional context. Biodiversity loss explained indirect effects in a region of intermediate productivity and was most damaging when land-use objectives favoured supporting and cultural services. In contrast, functional composition shifts, towards fast-growing plant species, strongly increased provisioning services in more inherently unproductive grasslands.

Keywords: Biodiversity-ecosystem functioning; ecosystem services; global change; land use; multifunctionality.

Figure 1

Ecosystem service weightings used to produce five measures of ecosystem multifunctionality according to scenarios representing different land‐use objectives. Scenarios are: (1) ‘production only’ with only provisioning services (forage production and quality); (2) ‘sustainable soils’ includes other functions promoting sustainable grass production; (3) ‘sustainable soils and crops’ additionally includes services benefitting surrounding croplands (pest and pathogen control and pollination); (4) ‘equal weight’ weights all processes equally and corresponds to classic multifunctionality measures; (5) ‘cultural multifunctionality’ weights cultural services highly, includes ecosystem functions associated with ecosystem health but does not include provisioning services (forage production and quality) or functions directly supporting production (potential nitrification and root decomposition). Weightings of 50% or 100% are indicated. Where we used different weightings, processes that were measures of final benefits for a particular scenario (e.g. forage production or aesthetic value) received weightings of 100% and functions which supported these were weighted at 50%.

Figure 2

The overall relationship between land‐use intensity (LUI) and ecosystem multifunctionality calculated for five scenarios, representing different land‐use objectives (Fig. 1), and three regions. These graphs show total effects of LUI on multifunctionality, i.e. direct + indirect effects. Lines show fits from a linear regression and slopes ± 1 SE are shown. Asterisks indicate significance levels ***P < 0.001, **P < 0.01, *P < 0.05. Note that y‐axes have been scaled to the maximum multifunctionality value possible for a given scenario, see the extended methods in the Supporting information.

Figure 3

The relationships between land‐use intensity (LUI), plant species richness and community‐weighted mean specific leaf area (SLA). (a, d, g) LUI and plant species richness (b, e, h) LUI and community‐weighted mean of SLA and (c, f, i) species richness and community weighted mean (CWM) SLA. The relationship is shown for the three regions (a–c) south‐west (d–f) central and (g–i) north‐east. Pearson correlation coefficients, r, are shown for each relationship.

Figure 4

The strength of direct and indirect land‐use effects on ecosystem multifunctionality. The index of multifunctionality was calculated for five scenarios, representing different land‐use objectives (Fig. 1), and three regions. The structural equation model used to calculate the indirect effects (a) through changing species richness and (e) through changing specific leaf area (SLA). Indirect effects could be mediated through changing species richness (b–d) or through changes to the community weighted mean (CWM) of SLA (f–h). The best explanation for the indirect effects (either SLA or species richness) for each region is shown by an asterisk (*) (see, Methods and Table S3). Indirect effects are calculated by multiplying the path coefficient for the effect of land‐use intensity (LUI) on species richness/SLA with the path coefficient for the effect of species richness/SLA on multifunctionality, see Table S4 for the individual path coefficients.