The taxon is accepted at species level: Lecanora conizaeoides

A well-known species that reflects major effects of past and present air-pollution (acid rain and nitrogen) on the lichen flora in Western Europe.

Native to lowland temperate Europe, rare in submontane Mediterranean Europe. Introduced in parts of North America, Australia and Asia (not on the map).

The species used to cover large parts of tree trunks in the West-European lowland. It is now rare and mainly occurs in natural areas.  The species is introduced in N America, but rarely reported and not present in large quantities. The decline in Europe is estimated as approximately 80% over the past 20 years, based on surveys of plots in the Netherlands (citation needed). This well-documented regional reduction is representative for W Europe, in similar monitoring studies in Belgium and Germany and UK mapping (citations needed). There is a continuing decline (https://www.verspreidingsatlas.nl/4303#) due to ongoing eutrophication from nitrogen pollution (Hauck, et al 2011). The population reduction is projected to continue, if it may be slowing slightly. Because the lowland European portion of the population is estimated at 40-50% of the total population, with an ongoing reduction of 80% over 20 years, the projected population reduction worldwide is estimated at 30-40%.

The twenty year time window reflects a time period of three generations in the mid-range of early colonizing lichens (6-8 years), including Lecanora conizaeoides.

Lecanora conizaeoides is a widespread lichen species that occurred in acid rain affected areas in entire Europe. The species has very much suffered from the decline of acid rain as a result of cleaner power plants and fuels since 1990. The species is also extremely sensitive to ammonia (nitrogen deposition), which caused a further decline. Both the decrease in acid rain and the increase of ammonia cause an increase in bark pH, the main factor causing the decline. Nowadays confined to coniferous trees and mature oak trees in (semi) open areas.

The main current threat is the high levels of ammonia (and other nitrogen compounds) from agro-industry and transportation. Major ammonia reduction measures were not able to stop the decline of this species and other acidophytes with a similar ecology.

Although the decline due to acid rain is not something we want to restore, reducing the widespread nitrogen deposition is still something that can help improve the situation of lichens growing on acid bark.

Continuation of existing monitoring schemes to estimate the population trend of this species and trends of other acidophytic and nitrophytic epiphytes.

Ahti, T. (1965). Notes on the distribution of Lecanora conizaeoides. The Lichenologist, 3(01), 91-92.

Aptroot, A., van Herk, K., & Sparrius, L. B. (2011). Basisrapport voor de Rode Lijst korstmossen. BLWG, Gouda.

BLWG (2016). NDFF Verspreidingsatlas: Lecanora conizaeoides - trend. http://www.verspreidingsatlas.nl/4303

Hauck, M., Otto, P. I., Dittrich, S., Jacob, M., Bade, C., Dörfler, I., & Leuschner, C. (2011). Small increase in sub-stratum pH causes the dieback of one of Europe’s most common lichens, Lecanora conizaeoides. Annals of botany, 108(2), 359-366.

LaGreca, S., & Stutzman, B. W. (2006). Distribution and ecology of Lecanora conizaeoides (Lecanoraceae) in eastern Massachusetts. The Bryologist, 109(3), 335-347.

Sparrius, L. B. (2007). Response of epiphytic lichen communities to decreasing ammonia air concentrations in a moderately polluted area of The Netherlands. Environmental Pollution 146: 375-379.

Stapper, N. J., & Franzen-Reuter, I. (2004). Mapping aerial hypertrophication with epiphytic lichens as biomonitors in North Rheine-Westphalia (NRW, Germany). Lichens in a changing pollution environment. English Nature Research Reports, 525, 31-36.

Van Haluwyn, C., & Van Herk, C. M. (2002). Bioindication: the community approach. In Monitoring with lichens—Monitoring Lichens (pp. 39-64). Springer Netherlands.

Van Herk, C. M. (2001). Bark pH and susceptibility to toxic air pollutants as independent causes of changes in epiphytic lichen composition in space and time. The Lichenologist, 33: 419-442.