Do We Have To Make Trade-Offs Between Biodiversity And Ecosystem Services?

Published on 5 August 2009 in Ecosystems and biodiversity

Introduction

Until recently, the impacts of agricultural change have been seen as a trade-off between productivity and biodiversity. However, there has been a general assumption that preserving biodiversity results in land also delivering a whole range of other ecosystem goods and services. These are defined as benefits that people and society gain from the wider environmental services that ecosystems can provide. The long-term supply of services from ecosystems underpins sustainability. These are grouped into four types:

Supporting services necessary for the production of all other ecosystem services;
Regulating services – society benefits from ecosystem regulation of climate, water quality and quantity etc;
Provisioning services - products such as food, fibre etc that society gets from ecosystems;
Cultural services - non-material benefits to society and individuals, e.g. aesthetic or spiritual benefits.

However, it is certainly possible that the provision of these ecosystem services may or may not be optimised alongside biodiversity. The latter is clearly the case with intensive farming where provisioning services are maximised and is largely incompatible with biodiversity conservation (except where field boundaries are managed sympathetically). There may be similar choices to be made between biodiversity and other ecosystem services, and hence the management of multi-functional landscapes becomes a matter of trade-offs and choices.

An example study system, a traditional crofting area on the west coast of Scotland where a wide range of land uses were available within a small area, was used to study the potential trade-offs between biodiversity and carbon sequestration. This is a key regulating service as plants remove atmospheric carbon dioxide and, under the right conditions, it can build up in the soil.

Key Points

Changing from traditional hay cropping (Figure 1) to any form of more intensive grazing or silage production resulted in a drop in biodiversity measured in terms of species richness of plants, beetles, and bees (Table 1).

Figure 1. Traditional hay meadow at Drumbuie, nr. Kyle of Lochalsh.

Only silage had a higher productivity than the meadows (Table1). There were no differences in the decomposition rate of standard litter between sites. Pasture and the abandoned sites had significantly poorer litter quality (higher LDMC) than the other land uses. This indicates that managing for soil carbon would identify silage, pasture or abandonment as suitable replacement management for hay cutting. However, this would be at the expense of species richness in all three surveyed groups for most of the transitions.

	Carbon				Diversity
	Productivity (P)	Litter quality (LQ)	Litter decomposition (LD)	Carbon f(P, LQ,LD,…)	Plants	Bees	Beetles
Silage	↑	=	=	↑	↓	↓	↑
Winter grazed	=	=	=	=	↓	=	=
Pasture	=	↓	=	↑	↓	↓↓	↓↓
Abandoned	=	↓	=	↑	↓↓	↓↓	↓

Table 1. A summary of changes in selected measures of carbon dynamics, overall prediction for carbon sequestration by soil and species richness on four alternative land use relative to traditional hay meadows.

Research Undertaken

Traditional hay-cropping is now a restricted land use. A range of land uses are possible when this practice is abandoned including silage making, conversion to pasture, abandonment and winter grazing.

Biodiversity assessments of ground beetles (Carabidae), bees and vascular plants were made on these land use types during the summer of 2007 on the National Trust for Scotland’s Balmacara Estate using standard methods.

Three indicators of carbon dynamics were assessed; above-ground net primary production, litter decomposition rate (assessed as the rate of breakdown of standard litter) and litter quality (assessed as community-weighted leaf dry matter content, which is inversely related to litter turnover).

Policy Implications

In some situations, such as filling in grips (drainage ditches) on moorland, there are clear benefits to biodiversity and to ecosystem services such as carbon sequestration as the moorland becomes wetter. In others, land use change can have negative effects on both biodiversity and certain services, such as the conversion of blanket bog to forestry. However, there are other scenarios, such as those tested here, where there appears to be no win-win situation that maximises a ‘key’ service and maximises biodiversity.

So far, analysing trade-offs has focussed on biodiversity and provisioning services, including the production of food, fibre and wood. In recent years managing land to ensure the regulation of water quality has become more common and studies are ongoing on their impact on biodiversity. As more focus is put on managing for other ecosystem services, such as for soil carbon sequestration, then the analysis of these trade-offs becomes more complex. This is because multiple goals have to be taken into account, as have the wishes of multiple stakeholders. Developing the tools and infrastructure to do this is necessary to ensure the efficient use of land for the provision of multiple services and the conservation of public goods such as biodiversity.

Author

Prof. Robin Pakeman r.pakeman@macaulay.ac.uk

Topics

Ecosystems and biodiversity