22/02/2017. Richard Smithers 1. Effects of pollutants from road traffic on natural habitats and risk to nature conservation sites Richard Smithers

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Effects of pollutants from road traffic on natural habitats and risk to nature conservation sites Richard Smithers Knowledge Leader (Ecosystems) 17 February 2017 Background Biodiversity 2020

1 Effects of pollutants from road traffic on natural habitats and risk to nature conservation sites Richard Smithers Knowledge Leader (Ecosystems) 17 February 2017 Background Biodiversity 2020 identifies air pollution as a direct threat to biodiversity. Many habitats of nature conservation importance are: Adapted to low nutrient conditions and/or are vulnerable to acidification Sensitive to additional airborne nitrogen oxides, sulphur dioxide and ammonia Sensitive to nitrogen and acid. Pollutants come from different sources, but transport is known to be the single largest source of nitrogen oxide emissions. Natural England commissioned Ricardo Energy & Environment to assess what risk air pollution from roads poses to sites of national or international importance. 2 Richard Smithers 1

Background 3 The ecological effects of air pollution from road transport Starting point: BIGNAL, K.L., ASHMORE, M.R. & POWER, S.A. 2004.

2 Background 3 The ecological effects of air pollution from road transport Starting point: BIGNAL, K.L., ASHMORE, M.R. & POWER, S.A The ecological effects of diffuse air pollution from road transport. English Nature Research Report 580. An update, which: Summarises peer-reviewed or grey literature published subsequently, particularly in relation to Natura 2000 Updates recommendations on remedies for tackling air pollution. 4 Richard Smithers 2

3 The ecological effects of air pollution from road transport Key issues and considerations Bignal and others (2004) when assessing impacts of air pollution from roads: Important to distinguish presence of elevated concentrations of substances (contamination) from evidence that concentrations have an adverse effect (pollution). Effects of pollutants may be cumulative over time. Biological responses may only become apparent when pollutants reach specific threshold concentrations. Effects of combinations of pollutants may be different from individual pollutants, so make it difficult to attribute effects to a particular component of exhaust emissions. Nevertheless, important implications, e.g. emissions of particles and carbon monoxide are high at low speeds, whereas nitrogen oxides increase rapidly at high speeds. Large variation in species sensitivity to air pollution, so road impacts may depend habitats close by. Effects of air pollutants may be substantially modified by local factors, such as climate, soils and management. 5 The ecological effects of air pollution from road transport Critical Levels and Critical Loads In addition, important to take into account whether air pollution from roads combines with other sources that may already approach/exceed Critical Levels or Critical Loads. Critical Levels: concentrations of pollutants in the atmosphere above which direct adverse effects on receptors, such as human beings, plants, ecosystems or materials, may occur according to present knowledge. Critical Loads: a quantitative estimate of exposure to one or more pollutants below which significant harmful effects on specified sensitive elements of the environment do not occur according to present knowledge Critical Loads for nitrogen are set empirically, using long-term data but for some habitats rely on expert judgment. Emmett and others (2011) detected some species impacts when nitrogen below Critical Loads, so may not protect all species, and continue above Critical Loads. 6 Richard Smithers 3

4 The ecological effects of air pollution from road transport Evidence of impacts of road transport pollution: roadside/field studies Bignal and others (2004) Few studies at different distances from roads and limited to effects on single species. No known studies looked before and after road construction to assess changes. Few studies near roads of different traffic density and, hence, pollution levels. Pollution levels not measured in many studies, or recorded for limited number of motor vehicle exhaust pollutants, so difficult to assess to critical levels. 7 Evidence of impacts of road transport pollution: roadside/field studies Effects on individual species Bignal and others (2004) Despite limited research, a number of clear effects of exposure to motor vehicle emissions that maybe applicable to many species: Effects on surface wax degradation, enzyme activity, physiology, chemistry and senescence. Responses attributed to exposure to volatile organic compounds, particulates, nitrogen oxides and ethylene, individually or in combination. 8 Richard Smithers 4

Evidence of impacts of road transport pollution: roadside/field studies Effects on individual species Since 2004: A number of transect studies of road traffic pollution impacts on species regarding

5 Evidence of impacts of road transport pollution: roadside/field studies Effects on individual species Since 2004: A number of transect studies of road traffic pollution impacts on species regarding nitrogen oxides, nitrogen and heavy metals. Further evidence that impacts of exposure to nitrogen oxides on individual species (e.g. increase in nitrogen-loving species, declines in tree health and lichen diversity) greatest within m from roads but discernible at greater distances. Further evidence that traffic emissions are a significant source of metal contamination but unlikely significant immediate toxic risk to plants. 9 Evidence of impacts of road transport pollution: roadside/field studies Effects on habitats and communities Bignal and others (2004) Few studies of effects on entire habitats or communities but recommended as species do not exist in isolation, thus, knock-on effects on the habitat or community. Motor vehicle pollution affects composition of heathland and lichen communities. 10 Richard Smithers 5

Evidence of impacts of road transport pollution: roadside/field studies Effects on habitats and communities Since 2004: Studies have investigated the effect of nitrogen emissions from road traffic on

6 Evidence of impacts of road transport pollution: roadside/field studies Effects on habitats and communities Since 2004: Studies have investigated the effect of nitrogen emissions from road traffic on habitats or communities. Suggest nitrogen oxides from road traffic emissions, rather than other forms of dry or wet nitrogen, are likely driver of changes in roadside plant communities, giving nitrogen-loving species a competitive advantage. 11 Evidence of impacts of road transport pollution: roadside/field studies Below-ground impacts Bignal and others (2004): Very limited evidence that road traffic pollutants (heavy metals and polycyclic aromatic hydrocarbons) affect tree fine-roots and soil microbes, which will affect nutrient cycling and ecosystem function. 12 Richard Smithers 6

7 Evidence of impacts of road transport pollution: roadside/field studies Below-ground impacts Since 2004: No new studies focused on below ground impacts but transect studies demonstrate heavy metals decline rapidly within 5 10m of roads and indiscernible beyond 50m. Transect studies perpendicular to motorways through a coniferous forest in Southern Germany (Bernhardt-Römermann and others 2006) found nitrates and ammonium in soils decreased up to 230m where influence of traffic was negligible. 13 Evidence of impacts of road transport pollution: roadside/field studies Impacts on plant-insect interactions Bignall and others (2004): Most studies on plant-insect interactions concentrate on road verges or central reservations, so difficult to assess extent of influence but: Some insects, e.g. aphids, appear to benefit from pollution-induced stress to roadside plants and an improved food source. Other insects suffer a poorer quality food source, e.g. due to metal contamination. Some insects, e.g. aphids, may benefit if predators cannot tolerate the roadside environment. Increase in insects that graze on plants contaminated with metals may impact the food chain, perhaps birds and small mammals. Increased insect herbivory can affect plant health through defoliation or stress. 14 Richard Smithers 7

8 Evidence of impacts of road transport pollution: roadside/field studies Impacts on plant-insect interactions Since 2004: Only located one additional study on impact of road traffic emissions on plantinsect interactions (Bignal and others 2007) Sessile oak and beech trees with greater insect damage up to 100m from motorways, increased nitrogen content reduced defences or increased palatability. Studies of individual plant species do not add weight to Bignall and others (2004) as metal concentrations unlikely significant immediate toxic risk to plants and Peachey and others (2009) note relatively low risk to primary consumers even in Central London parks. 15 Controlled fumigation and filtration studies Bignall and others (2004): Found few experiments using motor vehicle exhaust and used other studies of individual components to assess and predict impacts on habitats near roads. 16 Richard Smithers 8

Controlled fumigation and filtration studies Effects of vehicle exhaust Bignall and others (2004): Advantages of controlled fumigations over field-based studies is effects of pollutants can be

9 Controlled fumigation and filtration studies Effects of vehicle exhaust Bignall and others (2004): Advantages of controlled fumigations over field-based studies is effects of pollutants can be separated from other factors. Exposure to vehicle emissions at roadside concentrations affects plants: Growth, physiology, phenology and leaf surface characteristics Response to biotic and abiotic stresses In species-specific ways, positive/negative and changed over time And could lead to changes in competitive advantage and species composition near roads. But aphids did not respond the same as in the field, so may be additional factor(s) other than host plant food quality, e.g. the influence of salt from de-icing and/or reduced predation. 17 Controlled fumigation and filtration studies Effects of vehicle exhaust Since 2004: Only a handful of relevant studies using vehicle exhaust or its components. The effects of diesel exhaust emissions on: 12 herbaceous species included growth stimulation and inhibition, premature leaf senescence, delayed flowering; and changes in gas exchange (Honour and others 2009 and Bell and others 2011) Generation of hydroxyl (a free radical) reduced maximum photosynthetic rate and stomata conductance in Japanese red pine trees (Sakugawa and others 2011) Honeybees identification of floral odours, which may undermine foraging efficiency and pollination services. 18 Richard Smithers 9

10 Effects of specific road transport pollutants Nitrogen oxides Effects are seen in low concentrations for some species and so the impact arising from motor vehicles may be found tens to 100m or more from major roads (Bignal and others 2004) Since 2004, a study of seven plant species detected few significant effects, although above-ground biomass growth and root dry weight were reduced by up to 39% Combined evidence from fumigation experiments and transect studies suggests that nitrogen oxides are the key phytotoxic component of exhaust emissions. 19 Effects of specific road transport pollutants Volatile organic compounds Little evidence of ecological damage with the exception of ethylene (degraded leaf surface waxes, pigment bleaching and ultra-structural changes) (Bignal and others 2004). Since 2004, no new evidence found. Ammonia Emitted in small amounts by vehicles with catalytic converters, so roadside atmospheric concentrations are well below critical levels. Thus, gaseous ammonia unlikely to be a key issue (Bignal and others 2004). Since 2004, no new evidence found. Nitrogen Nitrogen oxides, ammonia and nitrous acid emissions from road traffic may all contribute to local nitrogen (Bignal and others 2004). 20 Richard Smithers 10

Effects of specific road transport pollutants Metals Metals are likely to persist in soils and levels may build up over time in the vicinity of roads (Bignal and others 2004).

11 Effects of specific road transport pollutants Metals Metals are likely to persist in soils and levels may build up over time in the vicinity of roads (Bignal and others 2004). Since 2004, no new evidence found. Particulates and dust Few attempts made to assess impacts of particulates and dust from motor vehicles on vegetation under controlled conditions, so difficult to assess (Bignal and others 2004). Since 2004, no new evidence found. 21 Methods to mitigate Wooded shelterbelts Bignal and others (2004) concluded that wooded shelterbelts effectively capture particulates, including their metal component, thereby reducing transport to sites further away from the road. Evidence since 2004 is more equivocal. Role in preventing spread of gaseous pollutants is less clear but may act as a physical barrier to nitrogen oxides by changing dispersal patterns. 22 Richard Smithers 11

12 Methods to mitigate Buffer zones Bignal and others (2004) concluded that buffer zones provide physical distance rather than remove pollutants from the atmosphere. Since 2004, no new evidence found but Bignal and others (2008) suggest new road building should avoid a buffer zone of m from sensitive sites. Compensatory habitat creation Mitigation by compensation of the effects of road transport pollutants is an alternative approach, but Bignal and others (2004) conclude re-creation of nutrient-poor habitats near roads is not recommended. Since 2004, no additional papers on compensatory habitat creation in relation to impact of air pollution from road transport. 23 Road traffic measures Traffic emissions essentially determined by three factors: Amount and type of vehicles flowing past a site Way vehicles are driven (e.g. their speed) and level of congestion Emissions performance of vehicles, dependent on age and technology. 24 Richard Smithers 12

13 Road traffic measures Reducing traffic flows Traffic restrictions and relocation Influencing travel behaviour 25 Road traffic measures Improving traffic flow and efficiency 26 Richard Smithers 13

14 Road traffic measures Improving traffic flow and efficiency Traffic control systems Road space design and management Driver education 27 Road traffic measures Promoting low emission vehicles Low emission zones Planning and infrastructure Partnership working and promotion 28 Richard Smithers 14

15 Risk of impacts of nitrogen oxides from road traffic on designated nature conservation sites Risk assessment methodology 29 Risk of impacts of nitrogen oxides from road traffic on designated nature conservation sites Classes of exposure to NOx High Exposure (background concentration + road contribution >30µg/m 3 in all cases) Medium (background concentration + road contribution > 25µg/m 3 but may or may not exceed 30µg/m 3 ) Low (background concentration + road contribution <25µg/m 3 in all cases) Qualifying scenarios High or Medium background + Large contribution High background + Large or Medium contribution Low background + Large contribution (where total >30µg/m 3 ) High background + Small contribution Medium background + Medium contribution Low background + Large or Medium contribution (where total >25µg/m 3 and <30µg/m 3 ) Low background + Small contribution Low background + Large or Medium contribution (where total <25µg/m 3 ) 30 Richard Smithers 15

Risk of impacts of nitrogen oxides from road traffic on designated nature conservation sites Exposure to NOx from road traffic The whole of each SSSI shaded according to the specific area of the site

16 Risk of impacts of nitrogen oxides from road traffic on designated nature conservation sites Exposure to NOx from road traffic The whole of each SSSI shaded according to the specific area of the site that was attributed the highest class of exposure Specific areas of each SSSI shaded according to their exposure class (i.e. areas within 50m of major roads or by individual 1km x 1km square) Exposure SSSIs SACs SSSIs SACs Total area (ha) Total no. of sites Total area (ha) Total no. of Sites Total area (ha) Total no. of sites Total area (ha) Total no. of sites High 41, , Medium 24, , Specific areas of sites (SSSIs and SACs) with High or Medium exposure to NO x from road traffic 31 Risk of impacts of nitrogen oxides from road traffic on designated nature conservation sites Classes of risk: nitrogen and acid Site sensitivity to N Exposure to NO x from traffic taking account of background concentrations High Medium Low above CL High (min. CL 5 or 8 kgn/ha/year) Medium (min. CL 10 or 15 kgn/ha/year ) Low (min. CL 20 kgn/ha/year ) No CL approaching CL (within 10%) not approaching CL above CL approaching CL (within 10%) not approaching CL above CL Potential risk of impacts matrix for nitrogen approaching CL (within 10%) not approaching CL Site sensitivity to acid Exposure to NOx from traffic taking account of background concentrations High Medium Low High (minclmaxn 0.3 to <1.0 keq/ha/year) Medium (minclmaxn 1.0 to <2.0 keq/ha/year) Low (minclmaxn 2.0 to 14.0 keq/ha/year) No CL above CL approaching CL (within 10%) not approaching CL above CL approaching CL (within 10%) not approaching CL above CL Potential risk of impacts matrix for acid approaching CL (within 10%) not approaching CL 32 Richard Smithers 16

Risk of impacts of nitrogen oxides from road traffic on designated nature conservation sites Risk of impacts from nitrogen & acid due to road traffic Exposure 2011 2020 High sensitivity, baseline N >

of Sites Area (ha) No. of sites Area (ha) No. of sites High 3027.8 23 11194.0 48 279.3 16 694.1 28 Medium 5944.5 3 4385.8 5 259.7 3 1465.

17 Risk of impacts of nitrogen oxides from road traffic on designated nature conservation sites Risk of impacts from nitrogen & acid due to road traffic Exposure High sensitivity, baseline N > Critical Load Medium sensitivity, baseline N > Critical Load High sensitivity, baseline N > Critical Load Medium sensitivity, baseline N > Critical Load Area (ha) No. of sites Area (ha) No. of Sites Area (ha) No. of sites Area (ha) No. of sites High Medium Exposure High sensitivity, baseline ac > Critical Load Medium sensitivity, baseline ac > Critical Load High sensitivity, baseline ac > Critical Load Medium sensitivity, baseline ac > Critical Load Area (ha) No. of sites Area (ha) No. of Sites Area (ha) No. of sites Area (ha) No. of sites High Medium Specific areas of SACs with High or Medium sensitivity where baseline exceeds Critical Loads and exposure to NO x from road traffic in combination with other sources is High or Medium 33 Risk of impacts of nitrogen oxides from road traffic on designated nature conservation sites How the work is being used by Natural England Evidence for use by external stakeholders as well as Natural England (e.g. Wildlife Trusts, Local Planning Authorities, Highways England) Evidence for plans to protect habitats and species pressure/ threat from nitrogen (e.g. Shared Nitrogen Action Plan pilots, Area Team focus areas) Providing a context for consideration of air quality impacts from road schemes Informing Natural England s discussions with Highways England in relation to air quality issues and air quality monitoring data. 34 Richard Smithers 17

18 Richard Smithers Knowledge Leader (Ecosystems) Richard Smithers 18

Air and Air Pollution Control Last changed: 4/04/11

http://www.umweltbundesamt.de/luft-e/eintraege-wirkungen/versauerung.htm Air and Air Pollution Control Last changed: 4/04/11 Air pollutant inputs Deposition Air pollutants not only have direct effects