Measuring the economic value of pollination services: Principles, evidence and knowledge gaps

An increasing degree of attention is being given to the ecosystem services which insect pollinators supply, and the economic value of these services. Recent research suggests that a range of factors are contributing to a global decline in pollination services, which are often used as a “headline” ecosystem service in terms of communicating the concept of ecosystem services, and how this ties peoples' wellbeing to the condition of ecosystems and the biodiversity found therein. Our paper offers a conceptual framework for measuring the economic value of changes in insect pollinator populations, and then reviews what evidence exists on the empirical magnitude of these values (both market and non-market). This allows us to highlight where the largest gaps in knowledge are, where the greatest conceptual and empirical challenges remain, and where research is most needed. & 2014 Elsevier B.V. All rights reserved. 1. Pollination: a headline ecosystem service? Animal pollination, usually via insects, birds or bats, influences the reproductive success of 87% of flowering plants world-wide (Ollerton et al., 2011). Worldwide, 1500 crops require insect pollination (Klein et al., 2007), and 3 to 8% of global crop production (in tonnage) depends on insect pollination (Aizen et al., 2009). In temperate regions, most animal pollination is provided by honeybees (Apis mellifera), bumblebees (Bombus spp.), solitary bees, wasps and hoverflies, while in the tropics, butterflies, moths, birds and bats become important (Klein et al., 2007). Some crops, such as oilseed rape, are effectively pollinated by a broad range of insects, while others are specialized for pollination by particular insects; for example cocoa (Theobroma cacao) is primarily pollinated by midges (Klein et al., 2007). A number of bee species are actively managed, most notably the honeybee. Managed bumblebees are most commonly used in enclosed production systems (glasshouses and poly-tunnels), but other managed species are predominantly used for field and orchard crops (eg apples and almonds). Globally, evidence is emerging that wild bees and other insects are more important to crop pollination than managed bees (Garibaldi et al., 2013, 2011). Since pollination is an ecosystem service which humans depend on through its link to world food production, it has become an often-cited example of how ecosystems services are economically valuable. The economic value flows from pollinators are both market and non-market valued. Market-valued benefits from pollinators consist of the contribution they make to the growing of a range of agricultural and horticultural crops (Gallai et al., 2009). Recent estimates suggest that crop pollination by insects underpins d430 million of crop production in the UK (Smith et al., 2011), with an equivalent figure of $361 bn worldwide (Lautenbach et al., 2012). However, there is considerable doubt over the precision, reliability, usefulness and interpretation of such figures. Non-market benefits derive from the utility which people derive from seeing pollinators or simply knowing they are being conserved and the indirect values derived from the aesthetic and cultural value of the wild flowers and garden plants which require pollination to sustain them. At any point in time, the present value of the future stream of marketand non-market valued benefits from pollinators, ie the value that can be derived in future, defines the value of this natural asset within a landscape. The ecosystem service values derived from pollinators depend to a large extent on the condition and extent of the stock of pollinators, which is part of an area's natural capital. The value of