This species is has been collected in a wide area but at very low numbers within a declining habitat type, namely, late successional to old growth forested wetlands. It is apparent that the species requires large, late decompositional down logs in basin wetlands. This habitat has documented decline in North America. For this reason, this species is being proposed as C-VU since its estimated total population is less than 10,000 mature individuals.
Helvella palustris Peck, Ann. Rep. N.Y. St. Mus. Nat. Hist. 33: 31 (1883) 
In spite of good morphological and microscopic characters, this species has some taxonomic uncertainty (Nyguyen et al 2013). This has been demonstrated by, for example, articles on Helvella relationships in Fungal Diversity (Zhao & Hyde 2015). This will need to be checked through adequate sequencing by mycologists familiar with the genus prior to confirming status of this taxon in the central and eastern United States. Based on the likelihood that the two outlier collections from Mt. Rainier, Washington, USA and Dovre, Norway collection is not this species (see for example Nyguyen et al 2013), these are being excluded from this assessment.
This species is very distinctly different from other Helvellas in having a non-lacunose, ribbed stipe and a very dark coloration overall; it has been collected at a number of sites across eastern North America, with one outlier in Washington state and one in Norway. The absence of more records suggests regional rarity and potential
Beug, Bessette & Bessette lists “eastern” (United States), Kuo repeats Smith’s description of “Michigan to New York” but there is also one record from Norway. It is suspected that this collection may be a different species.
MycoBank lists the following collections:
1879 NY (exotype, with holotype/isotype from1882 in Manlius, NY) by Peck in NYSF;
1896 July WI (Houghton), but possibly H. sulcata according to Burt, in WI
1930 - 1971 MI (variety of locales, 11 records, including sev. duplicate locales) by A.H. Smith in MICH
1934 PA (Stone Creek, rotten log) by Overholts in USDA - BPI
1935 VI (Hone Quarry Mountain, Rockingham Co., in soil) in USDA - BPI
1942 WA* (Mt. Rainier NP) Nancy Smith in MICH
1953, July NY (Bergen Swamp) Korf in CUP
1963 July MI (Ogamau Game Reserve) A.H. Smith in UBC
1963 July MI (Taquahmenon Falls S.P.) Brough in UBC
1964 Aug MI (Univ. of MI Biol Sta, Emmet Co.) by Rogerson in UBC
1968 Oct VI (Catoctin Mtn Pk, Thurmont) OK & Hope Miller in VPI
1973 MD (Frederick Co. no details) in USDA - BPI
1997 Norway*, Oppland, Dovre
2002 NH (Carroll Co., in forested swamp) - RVP (not accessioned)
* These two specimens may involved separate species and therefore should not be considered a part of the functional population.
This species is apparently widespread and mid-western to eastern, but rarely reported since 1970’s (50% from 1969 and 1971). There is an uncertain reason for a paucity of records in last 40 years; which may involve possible confusion with other Helvellas, although the habitat and morphology are fairly distinct. Habitat differences for H. palustris is forested wetlands, whereas H. sulcata is reported from and has been observed in uplands. Based on records and the available habitat for the extent of occurrence, estimated to be on the order of 5,000 - 10,000 mature individuals in widely scattered locales. This number has very likely declined on account of the loss of both old growth forests and wetlands in the region of occurrence.
Population Trend: Uncertain
The specific epithet for this species suggests swamps; Kuo further specifies as northern white-cedar swamps, although the single specimens in NH was found in a mixed hemlock-red maple swamp. Most collections in Mycobank were from Reese’s Bog in Cheboygan, MI and Wycamp Lake in Emmet, MI. Several of these records suggest old rotten logs, which is consistent with general published descriptions of the species, noting that the concept of H. sulcata is more common in uplands also on rotten logs. The determinant ecology may be the presence of well-decayed hardwood logs in or near swamps that are suitably sized to provide ample moisture for growth during the drier summer months while being elevated above the immediate water table. Such conditions would allow for adequate development of the mycorrhizal connection to swamp maples and potentially hemlock, and promote fruiting in the moist lignicolous material in summer and fall.
There are well-documented declines of old growth habitat with large, late decompositional stages of mossy logs that support this species. There are also good data of the loss of wetlands (i.e. USFWS estimated loss of 58% of freshwater wetlands in the US since colonization). There is also some threat from acidification from run-off that could affect the pH of basin wetlands where it occurs.
Recommended conservation actions include the protection of especially large, sub-boreal to temperate forested swamps and a minimum buffer of 100 feet from the edge of the wetland. Promoting the rarity of this organism could also stimulate further refinement on its distribution and the the possible permanent protection of sites where it occurs.
More distributional and observational data are needed. The taxonomy of this difficult group also needs to be subjected to sequencing scrutiny to compare, for example, the material from Washington and Norway versus those specimens from central and eastern North America.
Peck, Ann. Rep. N.Y. St. Mus. Nat. Hist. 33: 31 (1883) 
Kuo, @ http://www.mushroomexpert.com/helvella_palustris.html
Beug, Bessette & Bessette 2011. Ascomycete Fungi of North America. Austin: Univ. of Texas Press. p. 171.
Nyguyen et al. 2013. The Helvella lacunosa species complex in western North America: cryptic species, misapplied names and parasites. Mycologia 105(5): 1275 - 1286.
Hwang et al. 2015. Solving the ecological puzzle of mycorrhizal associations using data from annotated collections and environmental samples – an example of saddle fungi. Environmental Monitoring Reports 7(2):658-667.
Zhao & Hyde. 2015. Helvella pseudolacunosa Q. Zhao & K.D. Hyde, sp. nom prov. in Fungal Diversity (2015) 75:27–274