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When reading the Wikipedia entry on pistachio, I noticed that IUCN has classified the plant under "Near Threatened". On looking up its entry at IUCN, I see that its population is trending downwards, and it is "threatened by fruit collection, livestock grazing and cutting". The treat seems to have nothing to do with the often reported fungus. Looking up the yearly yields at Administrative Committee for Pistachios, I see that 2010 and 2012 were bumper years, but otherwise, I see no real trend of a decrease. Quite the contrary, I get the impression that the yearly yield is increasing. It's not as if the tree is difficult to grow, and we rely on trees growing in the wild; these trees are grown in orchards.

So, what's going on? Why would IUCN say that pistachio is Near Threatened?

prash
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    You cited the reason already yourself: "Threatened by fruit collection, livestock grazing and cutting". Obviously conservationists see this as a big enough threat to raise some alarm. – Chris Apr 12 '14 at 21:59
  • @Chris: What I wrote after that invalidates that reason: unflagging and even bumper yields. – prash Apr 12 '14 at 22:05
  • @prash It is near threatened and not endangered. I guess the IUCN sees this plant as going to face problems in the future due to a variety of reasons to which I would like to add habitat loss and temperature changes from changing weather patterns too. – The Last Word May 28 '14 at 11:08
  • @Chris You should post your comment as an answer. – fileunderwater Sep 11 '15 at 08:23

2 Answers2

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Short answer: They were talking about the wild species.

Using the presentation by a Farm Advisor and a Pomologist, Pistachio Cultivars as a rough indication of the state of the species, we see that the commercial crop does not have much diversity.

Probably 97% or more of the pistachio acreage in California is planted to the Pistacia vera female cultivar called ‘Kerman’ and a P. vera male called ‘Peters’.

The presentation mentions that other geographic regions prefer other cultivars. But generally, the the entire commercial population of pistachio seems to be limited to a few tens of cultivars.

The IUCN Red List that I cited in the question is rather poor on the details. However, the publication, Geneflow '06, included a report on Uzbekistan's pistachio:

Saving Central Asia’s pistachio diversity

For three millennia, pistachio trees were used in metallurgy and mining in Central Asia due to their accessibility and the highly calorific charcoal they produce. The result was a major depopulation of wild pistachio in the region. During the Stone Age, pistachio trees in Central Asia covered approximately 2 million hectares, compared with only 300 000 hectares today.

The loss of wild pistachio diversity in Central Asia has major implications for pistachio growers in the region and beyond. Most of the pistachio gene pool is to be found here, where it is needed to underpin the continued availability of the tasty nut.

All the reasons they cited as factors for threatening the species likely refers to the wild trees.

Community
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prash
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Pistachio populations don't appear to be decreasing from your research because you are looking at yields, not population level trends. Yield is not directly indicative of species health and is also not likely to immediately decrease with a population level decrease because farmers replant after loss.

The IUCN Red List Website lists declines in number of mature individuals, number of subpopulations, number of individuals in subpopulations, and number of individuals in the largest subpopulation. Other characteristics contributing to the "Near Threatened" classification are that the overall population is severely fragmented and both the overall population and subpopulations have been experiencing extreme fluctuations.

The IUCN lists the threats to the species as: "Natural stands have been impacted by overgrazing and are considered unproductive (Trees and Shrubs Online 2020), which may impact their management. Wild trees are also under threat from cutting and fruit collecting (Eastwood et al. 2009), while historically, the wild population has been reduced due to trees being felled for timber (Khanazarov et al. 2009). Human development has also led to habitat loss in some regions, though the extent of the impacts these actions have had across the species range are not clear."

Source: https://www.iucnredlist.org/species/63497/61526633#population

I also imagine that there is concern about species diversity. According to https://www.gbif.org/species/3190585 Pistacia vera is dominating the gene pool and population, which makes makes the sustainability of the Species unstable. If a pathogen were to target Pistacia vera, the impact on the Species could be devastating.

Mary Nell Armstrong
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  • It's not clear what the sources "Trees and Shrubs Online 2020", "Eastwood et al. 2009", or "Khanazarov et al. 2009" refer to: more information is needed, like a DOI or URL, a title, a journal/book, etc. – Bryan Krause Oct 13 '23 at 23:17