Joanna Isobel House

Ecosystem service supply and vulnerability to global change in Europe

Global change will alter the supply of ecosystem services that are vital for human well-being. To investigate ecosystem service supply during the 21st century, we used a range of ecosystem models and scenarios of climate and land-use change to conduct a Europe-wide assessment. Large changes in climate and land use typically resulted in large changes in ecosystem service supply. Some of these trends may be positive (for example, increases in forest area and productivity) or offer opportunities (for example, “surplus land” for agricultural extensification and bioenergy production). However, many changes increase vulnerability as a result of a decreasing supply of ecosystem services (for example, declining soil fertility, declining water availability, increasing risk of forest fires), especially in the Mediterranean and mountain regions.

Recent patterns and mechanisms of carbon exchange by terrestrial ecosystems

Knowledge of carbon exchange between the atmosphere, land and the oceans is important, given that the terrestrial and marine environments are currently absorbing about half of the carbon dioxide that is emitted by fossil-fuel combustion. This carbon uptake is therefore limiting the extent of atmospheric and climatic change, but its long-term nature remains uncertain. Here we provide an overview of the current state of knowledge of global and regional patterns of carbon exchange by terrestrial ecosystems. Atmospheric carbon dioxide and oxygen data confirm that the terrestrial biosphere was largely neutral with respect to net carbon exchange during the 1980s, but became a net carbon sink in the 1990s. This recent sink can be largely attributed to northern extratropical areas, and is roughly split between North America and Eurasia. Tropical land areas, however, were approximately in balance with respect to carbon exchange, implying a carbon sink that offset emissions due to tropical deforestation. The evolution of the terrestrial carbon sink is largely the result of changes in land use over time, such as regrowth on abandoned agricultural land and fire prevention, in addition to responses to environmental changes, such as longer growing seasons, and fertilization by carbon dioxide and nitrogen. Nevertheless, there remain considerable uncertainties as to the magnitude of the sink in different regions and the contribution of different processes.

Long-term sensitivity of soil carbon turnover to warming

The sensitivity of soil carbon to warming is a major uncertainty in projections of carbon dioxide concentration and climate. Experimental studies overwhelmingly indicate increased soil organic carbon (SOC) decomposition at higher temperatures, resulting in increased carbon dioxide emissions from soils. However, recent findings have been cited as evidence against increased soil carbon emissions in a warmer world. In soil warming experiments, the initially increased carbon dioxide efflux returns to pre-warming rates within one to three years, and apparent carbon pool turnover times are insensitive to temperature. It has already been suggested that the apparent lack of temperature dependence could be an artefact due to neglecting the extreme heterogeneity of soil carbon, but no explicit model has yet been presented that can reconcile all the above findings. Here we present a simple three-pool model that partitions SOC into components with different intrinsic turnover rates. Using this model, we show that the results of all the soil-warming experiments are compatible with long-term temperature sensitivity of SOC turnover: they can be explained by rapid depletion of labile SOC combined with the negligible response of non-labile SOC on experimental timescales. Furthermore, we present evidence that non-labile SOC is more sensitive to temperature than labile SOC, implying that the long-term positive feedback of soil decomposition in a warming world may be even stronger than predicted by global models.

Beyond Predictions: Biodiversity Conservation in a Changing Climate

Climate change is predicted to become a major threat to biodiversity in the 21st century, but accurate predictions and effective solutions have proved difficult to formulate. Alarming predictions have come from a rather narrow methodological base, but a new, integrated science of climate-change biodiversity assessment is emerging, based on multiple sources and approaches. Drawing on evidence from paleoecological observations, recent phenological and microevolutionary responses, experiments, and computational models, we review the insights that different approaches bring to anticipating and managing the biodiversity consequences of climate change, including the extent of species’ natural resilience. We introduce a framework that uses information from different sources to identify vulnerability and to support the design of conservation responses. Although much of the information reviewed is on species, our framework and conclusions are also applicable to ecosystems, habitats, ecological communities, and genetic diversity, whether terrestrial, marine, or fresh water.

Global change pressures on soils from land use and management

Soils are subject to varying degrees of direct or indirect human disturbance, constituting a major global change driver. Factoring out natural from direct and indirect human influence is not always straightforward, but some human activities have clear impacts. These include land-use change, land management and land degradation (erosion, compaction, sealing and salinization). The intensity of land use also exerts a great impact on soils, and soils are also subject to indirect impacts arising from human activity, such as acid deposition (sulphur and nitrogen) and heavy metal pollution. In this critical review, we report the state-of-the-art understanding of these global change pressures on soils, identify knowledge gaps and research challenges and highlight actions and policies to minimize adverse environmental impacts arising from these global change drivers. Soils are central to considerations of what constitutes sustainable intensification. Therefore, ensuring that vulnerable and high environmental value soils are considered when protecting important habitats and ecosystems, will help to reduce the pressure on land from global change drivers. To ensure that soils are protected as part of wider environmental efforts, a global soil resilience programme should be considered, to monitor, recover or sustain soil fertility and function, and to enhance the ecosystem services provided by soils. Soils cannot, and should not, be considered in isolation of the ecosystems that they underpin and vice versa. The role of soils in supporting ecosystems and natural capital needs greater recognition. The lasting legacy of the International Year of Soils in 2015 should be to put soils at the centre of policy supporting environmental protection and sustainable development.

CO2 emissions from land‐use change affected more by nitrogen cycle, than by the choice of land‐cover data

The high uncertainty in land-based CO2 fluxes estimates is thought to be mainly due to uncertainty in not only quantifying historical changes among forests, croplands, and grassland, but also due to different processes included in calculation methods. Inclusion of a nitrogen (N) cycle in models is fairly recent and strongly affects carbon (C) fluxes. In this study, for the first time, we use a model with C and N dynamics with three distinct historical reconstructions of land-use and land-use change (LULUC) to quantify LULUC emissions and uncertainty that includes the integrated effects of not only climate and CO2 but also N. The modeled global average emissions including N dynamics for the 1980s, 1990s, and 2000-2005 were 1.8 ± 0.2, 1.7 ± 0.2, and 1.4 ± 0.2 GtC yr(-1) , respectively, (mean and range across LULUC data sets). The emissions from tropics were 0.8 ± 0.2, 0.8 ± 0.2, and 0.7 ± 0.3 GtC yr(-1) , and the non tropics were 1.1 ± 0.5, 0.9 ± 0.2, and 0.7 ± 0.1 GtC yr(-1) . Compared to previous studies that did not include N dynamics, modeled net LULUC emissions were higher, particularly in the non tropics. In the model, N limitation reduces regrowth rates of vegetation in temperate areas resulting in higher net emissions. Our results indicate that exclusion of N dynamics leads to an underestimation of LULUC emissions by around 70% in the non tropics, 10% in the tropics, and 40% globally in the 1990s. The differences due to inclusion/exclusion of the N cycle of 0.1 GtC yr(-1) in the tropics, 0.6 GtC yr(-1) in the non tropics, and 0.7 GtC yr(-1) globally (mean across land-cover data sets) in the 1990s were greater than differences due to the land-cover data in the non tropics and globally (0.2 GtC yr(-1) ). While land-cover information is improving with satellite and inventory data, this study indicates the importance of accounting for different processes, in particular the N cycle.

Trees and biomass energy: Carbon storage and/or fossil fuel substitution?

Abstract Studies on climate change and energy production increasingly recognise the crucial role of biological systems. Carbon sinks in forests (above and below ground), C02 emissions from deforestation, planting trees for carbon storage, and biomass as a substitute for fossil fuels are some of the key issues which arise. This paper assesses various forestry strategies and examines land availability, forest management, environmental sustainability, social and political factors, infrastructure and organisation, economic feasibility, and ancillary benefits associated with biomass for energy. Halting deforestation is of paramount importance and should have priority above all other options, although it will not be easy to implement for a variety of well known reasons. There is also great potential for reforestation of degraded lands, agroforestry and improved forest management. We conclude biomass energy plantations and other types of energy cropping could be a more effective strategy for carbon mitigation than simply growing trees as a carbon store, particularly on higher productivity lands. Use of the biomass produced as an energy source has the added advantage of a wide range of other environmental, social and economic benefits. The constraints to achieving environmentally-acceptable biomass production are not insurmountable. Rather they should be seen as scientific and entrepreneurial opportunities which will yield numerous advantages in the long term.

Biomass energy in Western Europe to 2050

Abstract Presently biomass energy supplies at least 2 EJ/yr (47 Mtoe) in OECD Europe, which is about 4% of total primary energy consumption (54.1 EJ). Estimates of the potential for bioenergy in the next century range from 2 to 20 EJ/yr. This paper estimates a potential of 9.0–13.5 EJ in 2050, which represents 17–30% of projected total energy requirements. This depends on assumptions of available land areas, achievable yields and the amount of recoverable residues utilized. Greater environmental and net energy benefits can be derived from perennial and woody energy crops compared to annual arable crops as alternative feedstocks for fossil fuels. The relative contribution of biofuels in the future will ultimately depend on markets and incentives, on R&D progress and on environmental requirements.

Utilising biomass crops as an energy source : a European perspective

Biomass can be grown to act as a carbon (C) store, or as a direct substitute for fossil fuels (with no net contribution to atmospheric CO2 if produced and used sustainably). There is great potential for the modernisation of biomass fuels to produce convenient energy carriers such as electricity and liquid fuels. Bioenergy accounts for about 15% of primary energy used throughout the world, and 4% of energy used in Western Europe. Several European countries plan to significantly increase their use of bioenergy and some already obtain over 10% of their energy from biomass fuels. The European Community (EC) is planning to implement policies which will more than double the use of biomass by 2005, with biofuels taking 5% of the motor vehicle fuel market, and a resultant reduction in CO2 emissions of about 180 million tonnes (Mt), equivalent to 50 Mt C/yr. The potential contribution of biofuels is even greater, especially with all the ‘set-aside’ land being taken out of production. Use of 15–20 million hectares (Mha) of agricultural land for biomass crops could represent an annual sink of some 90–120 Mt C or else offset between 50 Mt C and 120 Mt C from fossil fuel emissions, depending on the fuel displaced (7–17% of total EC carbon emissions). Policies are needed that will encourage the penetration of biofuels into the market such as increased support for research, development and demonstration, subsidies for biofuels, and carbon taxes on fossil fuels.

How can land-use modelling tools inform bioenergy policies?

Targets for bioenergy have been set worldwide to mitigate climate change. Although feedstock sources are often ambiguous, pledges in European nations, the United States and Brazil amount to more than 100 Mtoe of biorenewable fuel production by 2020. As a consequence, the biofuel sector is developing rapidly, and it is increasingly important to distinguish bioenergy options that can address energy security and greenhouse gas mitigation from those that cannot. This paper evaluates how bioenergy production affects land-use change (LUC), and to what extent land-use modelling can inform sound decision-making. We identified local and global internalities and externalities of biofuel development scenarios, reviewed relevant data sources and modelling approaches, identified sources of controversy about indirect LUC (iLUC) and then suggested a framework for comprehensive assessments of bioenergy. Ultimately, plant biomass must be managed to produce energy in a way that is consistent with the management of food, feed, fibre, timber and environmental services. Bioenergy production provides opportunities for improved energy security, climate mitigation and rural development, but the environmental and social consequences depend on feedstock choices and geographical location. The most desirable solutions for bioenergy production will include policies that incentivize regionally integrated management of diverse resources with low inputs, high yields, co-products, multiple benefits and minimal risks of iLUC. Many integrated assessment models include energy resources, trade, technological development and regional environmental conditions, but do not account for biodiversity and lack detailed data on the location of degraded and underproductive lands that would be ideal for bioenergy production. Specific practices that would maximize the benefits of bioenergy production regionally need to be identified before a global analysis of bioenergy-related LUC can be accomplished.