Robbie M. Andrew

The challenge to keep global warming below 2 °C

The latest carbon dioxide emissions continue to track the high end of emission scenarios, making it even less likely global warming will stay below 2 °C. A shift to a 2 °C pathway requires immediate significant and sustained global mitigation, with a probable reliance on net negative emissions in the longer term.

CONSTRUCTING AN ENVIRONMENTALLY-EXTENDED MULTI-REGIONAL INPUT–OUTPUT TABLE USING THE GTAP DATABASE

The use of Multi-Regional Input–Output Analysis (MRIOA) for understanding global environmental problems is growing rapidly. Renewed interest in MRIOA has led to several large research projects focused on constructing detailed and accurate MRIOTs. However, very few researchers have made use of the already available and regularly updated database produced by the Global Trade Analysis Project (GTAP). We demonstrate and discuss how the GTAP database can be converted into an MRIOT without the need for additional balancing. An illustrative example uses the GTAP-MRIO to reallocate carbon dioxide emissions from producing to consuming countries. We suggest that an MRIOT that treats international transport exogenously is adequate until more reliable data on international transport margins and emissions are available. To focus resources and refine methods, a concerted research effort is needed to compare the results of the GTAP-MRIO model with the new MRIO datasets under development.

Modelling nitrous oxide emissions from dairy-grazed pastures

Soil N2O emissions were measured during four seasons from two highly productive grass-clover dairy pastures to assess the influences of soil moisture, temperature, availability of N (NH4+ and NO3–) and soluble C on N2O emissions, and to use the emission data to validate and refine a simulation model (DNDC). The soils at these pasture sites (Karapoti fine sandy loam, and Tokomaru silt loam) differed in texture and drainage characteristics. Emission peaks for N2O coincided with rainfall events and high soil moisture content. Large inherent variations in N2O fluxes were observed throughout the year in both the ungrazed (control) and grazed pastures. Fluxes averaged 4.3 and 5.0 g N2O/ha/day for the two ungrazed sites. The N2O fluxes from the grazed sites were much higher than for the ungrazed sites, averaging 26.4 g N2O/ha/day for the fine sandy loam soil, and 32.0 g N2O/ha/day for the silt loam soil. Our results showed that excretal and fertiliser-N input, and water-filled pore space (WFPS) were the variables that most strongly regulated N2O fluxes. The DNDC model was modified to include the effects of day length on pasture growth, and of excretal-N inputs from grazing animals; the value of the WFPS threshold was also modified. The modified model ‘NZ-DNDC’ simulated effectively most of the WFPS and N2O emission pulses and trends from both the ungrazed and grazed pastures. The modified model fairly reproduced the real variability in underlying processes regulating N2O emissions and could be suitable for simulating N2O emissions from a range of New Zealand grazed pastures. The NZ-DNDC estimates of total yearly emissions of N2O from the grazed and ungrazed sites of both farms were within the uncertainty range of the measured emissions. The measured emissions changed with changes in soil moisture resulting from rainfall and were about 20% higher in the poorly drained silt loam soil than in the well-drained sandy loam soil. The model accounts for these climatic variations in rainfall, and was also able to pick up differences in emissions resulting from differences in soil texture.

A MULTI-REGION INPUT–OUTPUT TABLE BASED ON THE GLOBAL TRADE ANALYSIS PROJECT DATABASE (GTAP-MRIO)

Understanding the drivers of many environmental problems requires enumerating the global supply chain. Multi-region input–output analysis (MRIOA) is a well-established technique for this purpose, but constructing a multi-region input–output table (MRIOT) can be a formidable challenge. We constructed a large MRIOT using the Global Trade Analysis Project (GTAP) database of harmonised economic, IO, and trade data. We discuss the historical development of the GTAP-MRIO and describe its efficient construction. We provide updated carbon footprint estimates and analyse several issues relevant for MRIO construction and applications. We demonstrate that differences in environmental satellite accounts may be more important than differences in MRIOTs when calculating national carbon footprints. The GTAP-MRIO is a robust global MRIOT and, given its easy availability and implementation, it should allow the widespread application of global MRIOA by a variety of users.

Attribution of CO2 emissions from Brazilian deforestation to consumers between 1990 and 2010

Efforts to reduce deforestation to mitigate climate change and to conserve biodiversity are taking place on a global scale. While many studies have estimated the emissions occurring from deforestation, few studies have quantified the domestic and international drivers sustaining deforestation rates. In this study we establish the link between Brazilian deforestation and production of cattle and soybeans, and allocate emissions between 1990 and 2010 along the global supply chain to the countries that consume products dependent on Brazilian deforestation. We find that 30% of the carbon emissions associated with deforestation were exported from Brazil in the last decade, of which 29% were due to soybean production and 71% cattle ranching. The share exported is growing, with industrialized nations and emerging markets (especially Russia and China) greatly increasing imports. We find a correlation between exports (and hence global consumption) of Brazilian cattle and soybeans and emissions from deforestation. We conclude that trade is emerging as a key driver of deforestation in Brazil, and this may indirectly contribute to loss of the forests that industrialized countries are seeking to protect through international agreements.

Assessment of multiple ecosystem services in New Zealand at the catchment scale

The ecosystem services approach to resource management considers all services provided by ecosystems to all sections of the community. As such, it could be used to assess sustainability of human development and equity in resource use. To facilitate the approach, tools are required at the level of detail at which policy and management decisions are made. We have developed spatially explicit models of indicators of important ecosystem services in New Zealand: regulation of climate, control of soil erosion, regulation of water flow (quantity), provision of clean water (quality), provision of food and fibre, and provision of natural habitat. The models were developed using lookup tables from process-based models to allow rapid evaluation of land-use scenarios. We demonstrate the application of the models to assess ecosystem services in a simulation of hill-country afforestation in the Manawatu catchment, which has recently seen increasing soil erosion in the hills leading to sedimentation of waterways. Each ecosystem service was assessed by calculating the change in the indicator relative to two extremes. The ecosystem services with the largest relative changes were control of soil erosion, carbon sequestration, and provision of wood.

Climate policy and dependence on traded carbon

A growing number of countries regulate carbon dioxide (CO2) emissions occurring within their borders, but due to rapid growth in international trade, the products consumed in many of the same countries increasingly rely on coal, oil and gas extracted and burned in other countries where CO2 is not regulated. As a consequence, existing national and regional climate policies may be growing less effective every year. Furthermore, countries that are dependent on imported products or fossil fuels are more exposed to energy and climate policies in other countries. We show that the combined international trade in carbon (as fossil fuels and also embodied in products) increased from 12.3 GtCO2 (55% of global emissions) in 1997 to 17.6 GtCO2 (60%) in 2007 (growing at 3.7% yr−1). Within this, trade in fossil fuels was larger (10.8 GtCO2 in 2007) than trade in embodied carbon (6.9 GtCO2), but the latter grew faster (4.6% yr−1 compared with 3.1% yr−1 for fuels). Most major economies demonstrate increased dependence on traded carbon, either as exports or as imports. Because energy is increasingly embodied in internationally traded products, both as fossil fuels and as products, energy and climate policies in other countries may weaken domestic climate policy via carbon leakage and mask energy security issues.

Towards real-time verification of CO2 emissions

The Paris Agreement has increased the incentive to verify reported anthropogenic carbon dioxide emissions with independent Earth system observations. Reliable verification requires a step change in our understanding of carbon cycle variability.

Life-cycle energy and CO2 analysis of stormwater treatment devices

Environmental impacts associated with the construction, maintenance, and disposal of low-impact stormwater management devices are one aspect that should be considered during decision-making and life-cycle assessment (LCA) is a suitable method for quantifying such impacts. This paper reports a pilot study that employs LCA to compare life-cycle energy requirements and CO2 emissions of two stormwater devices in New Zealand. The two devices are a raingarden servicing an urban feeder road, and a sand filter that could have been installed in its stead. With an assumed life-time of 50 years, the life-cycle energy requirements of the built raingarden were almost 20% less than for the sand filter, while the CO2 emissions were 30% less. Our analysis shows that given the difference between the infiltration rates used in the raingarden design (0.3 m/day) and measured during monitoring (3 m/day) there was potential to make significantly greater life-time savings using a smaller design for the raingarden that would have also met the treatment efficiency expectations. The analysis highlights the significant contribution of transportation-of both materials and staff-and ongoing maintenance to a treatment devices life-cycle energy and CO2 profiles.

A distributed model of water balance in the Motueka catchment, New Zealand

A distributed water balance model is used to simulate the soil moisture regime of the Motueka catchment. The model is a major simplification of the Distributed Hydrology-Vegetation-Soil Model (DHVSM) with modifications suitable for the study area. The model was applied at 25-m resolution with a 1-day time-step for 10 years. The simulated hydrograph showed good correspondence with the observed hydrograph and there was good agreement of simulated and measured mean annual discharges (57.3m^3s^-^1 as compared with 58.7m^3s^-^1). Five different land cover scenarios were used to predict the effects of vegetation change on the hydrological regime: (1) current land cover; (2) prehistoric land cover; (3) maximum pine planting; (4) pine trees on easy slopes; and (5) pine trees on steep slopes. The pine scenarios all reduced the mean annual flow by about 2m^3s^-^1, while the prehistoric scenario reduced the mean annual flow by about 6m^3s^-^1. The pine scenarios (3, 4, and 5) reduced the 7-day 5-year low flow from 7.4m^3s^-^1 to between 6.5m^3s^-^1 and 6.8m^3s^-^1, respectively; and the prehistoric scenario reduced the 7-day 5-year low flow to 5.3m^3s^-^1.