ELKHORN SLOUGH FOUNDATION

Financials

From the e-filed returns the IRS publishes as XML (latest three processing years; amended returns replace the original). PDF copies at the IRS.

Officers, directors and key employees

As listed on the 990 for the year ended June 30, 2025, highest compensation first.

Address and contacts

Address (IRS master file)

PO BOX 267, MOSS LANDING, CA 95039-0267

Principal officer (990 for 2024)

Mark Silberstein, PO Box 267, Moss Landing, CA 95039

Signed the 990

Mark Silberstein, Executive Director

Phone

(831) 728-5939

Website

http://www.elkhornslough.org/

Return prepared by

CliftonLarsonAllen LLP

California records

California keeps its own records of charities and corporations. Search them by EIN 94-2823247 or by the name ELKHORN SLOUGH FOUNDATION.

Attorney General, Registry of Charities and Fundraisers

Registration status and filed reports (CT-TR-1, RRF-1)

Secretary of State, bizfile Online

Corporation status, entity number, agent for service

Franchise Tax Board

Entity status letter (state tax exemption, good standing)

Mission

The Elkhorn Slough Foundation's mission is to conserve and restore Elkhorn Slough and its watershed, California's largest tidal salt marsh south of San Francisco Bay. Renowned for its extraordinary biodiversity, Elkhorn Slough features a dynamic working landscape intertwined with rich natural habitats. To achieve its mission, the Elkhorn Slough Foundation focuses on the direct acquisition and stewardship of key lands while collaborating with partnerorganizations and agencies. Together, they advance sound scientific research, deliver impactful education programs, and foster meaningful community engagement. As an accredited organization through the Land Trust Alliance Accreditation Commission, the Foundation upholds the highest standards in conservation and land stewardship.

Program accomplishments

• The Research and Monitoring (RAM) program on the Elkhorn Slough National Estuarine Research Reserve (ESNERR) is the primary vehicle for conducting water quality monitoring, habitat monitoring, and biological monitoring on the Reserve and throughout the Elkhorn Slough Watershed. The research and monitoring team has also been responsible for the publication of a series of peer-reviewed scientific publications, listed on the website: https://elkhornslough.org/reserve/research. This is an ongoing program funded by grants from NOAA and various state and federal agencies supporting restoration science. Elkhorn Slough Foundation administers these funds for the benefit of ESNERR and slough conservation in concert with the California Department of Fish and Wildlife. During the FY24-25 fiscal year, the Research team co-authored ten papers in scientific journals, studied metal contamination resulting from the Moss Landing Battery Fire, and continued to conduct marsh and oyster restoration in partnership with a local Tribe.
  Expenses $970,779
• The Tidal Wetland Program (TWP) is a multi-agency effort addressing one of the most critical ecological challenges in the tidal portions of Elkhorn Slough: the dramatic loss of vegetated marshland caused by historic modifications to the slough's hydrology. Collaborating with over 100 scientists, resource managers, local residents, and other stakeholders, TWP has employed an ecosystem-based management approach to halt habitat loss and restore natural functions to the slough system. This effort has resulted in the implementation of more natural tidal flow to the Parson's Slough complex and Whistlestop within the Elkhorn Slough National Estuarine Research Reserve, protecting over 450 acres of tidal wetlands and keeping public access to the main channel of the slough open.Ongoing work focuses on restoring wetlands through the beneficial reuse of clean sediments to rebuild subsided marshes, while also exploring the potential for carbon sequestration in these restored habitats. One key initiative, the Hester Marsh restoration, is revitalizing 150 acres of formerly diked and degraded marsh. This project involves elevating the subsided marsh plain by adding soil and bringing it to the upper end of the tidal frame to support marsh vegetation. The elevation is designed to accommodate projected sea-level rise well into the next century. Looking ahead, the Tidal Wetland Program plans to integrate infrastructure resilience into its broader ecosystem resilience efforts.
  Expenses $1,500,877
• The Land Stewardship Program oversees the restoration, maintenance, and management of more than 5,900 acres within the Elkhorn Slough watershed. Over the past year, the Stewardship team collaborated with dozens of community volunteers and the California Conservation Corps to carry out a diverse range of conservation efforts. These activities included removing tons of trash and debris, controlling invasive weed species, monitoring key lands and wildlife, mapping natural resources, and propagating native plants. Through this work, the program has successfully transformed hundreds of acres of degraded landscapes, such as eroded sandhills, former eucalyptus groves, and abandoned farmland, into thriving, healthy habitats. Simultaneously, the program preserves the intact natural areas of the slough, ensuring their ecological vitality for the future. In the last fiscal year, the team achieved major milestones, including producing and out-planting millions of native seeds, highlighted by an 8-acre seeding project in the Hester grassland, and removing over 30 acres of fire-prone, invasive eucalyptus trees to reduce catastrophic wildfire risk and protect native plants and animals.
  Expenses $1,055,668
• Since 1982, the Elkhorn Slough Foundation (ESF) has led efforts to conserve and restore Elkhorn Slough and its watershed. Through the Land Acquisition program, ESF has protected over four thousand acres of key lands through an active program of acquiring fee and easement interests in properties in the watershed. Public interest conservation values secured by these acquisitions include open space, wildlife and rare species habitat, viewshed protection, groundwater recharge, and water quality improvement. By working in close collaboration with other agencies and organizations, ESF has been able to expand funding and support for Elkhorn Slough protection and conservation management. In the 2024-'25 fiscal year our accomplishments include: 1) renewed our accreditation with the Land Trust Accreditation Commission, 2) added a new strategic objective to protect wildlife connectivity to the upper watershed, 3) mapped and analyzed five properties totaling about 900 acres in the new connectivity area for potential acquisition, and 4) made steady progress on several transactions in the watershed totaling about 1,500 acres to protect wetlands, grasslands, oak woodland and sustainable farmland.
  Expenses $153,358
• ESF's Education and Public Relations Program (EPR) includes a vibrant social media presence and various public talks, walks, and programs designed for school and community groups. Each year, we support more than 20 outside organizations by providing volunteer opportunities for groups such as Scouting America, church groups, school groups, corporate volunteer programs, and more. Our outdoor education program engages over 150 local students by helping them build meaningful relationships with their peers and the natural environment. For example, students from Hall Elementary School have the opportunity to regularly experience open spaces through ~15 half-day visits per school year. In 2025, we doubled the number of local university students involved in our community programs from 23 to 46. These students, from California State University Monterey Bay, are completing Community Engagement Capstone Projects by helping us deliver programming to elementary school students and families in the community. Among other things, these students are learning how to develop culturally relevant programs that are consciously co-designed with participants, connecting families to the land and water in their communities through projects that remove barriers to access.We also continue to strengthen partnerships with like-minded organizations to conserve and restore Elkhorn Slough and educate the community about its ecological significance. This includes active participation in Juntxs En La Naturaleza, a collaborative group that includes the Monterey Bay Aquarium, Bird School Project, Latino Outdoors, Puentes Nature, Milpa, Regeneracion, and others. Together, we provide access to nature for 300+ historically underserved families in our community. Additionally, we support education and volunteer programs at the Elkhorn Slough Reserve, which served 2,750 students and 21,000 visitors in 2025.
  Expenses $535,723 · grants $6,491 · revenue $61,853
• The Training and Engagement Program (TE) is an ongoing ESNERR program, funded primarily by NOAA, that partners with other organizations to bring together diverse participants, including farmers, ranchers, private and public land managers, conservationists, regulatory and agency personnel, and scientists, to discuss and explore solutions to key natural resource management issues within the Central Coast region. TE also offers a suite of highly sought-after trainings on the biology and management of threatened and endangered wildlife species, such as California tiger salamanders, foothill yellow-legged frog, and western burrowing owls. In FY2024-2025, TE hosted or co-hosted seven training workshops that brought together approximately 380 environmental professionals and community members. TE builds collaborative networks that develop expertise and leadership to better conserve natural and working lands throughout the Elkhorn Slough watershed, the Central Coast region, and statewide.
  Expenses $193,762 · grants $2,500

What it must file and when

IRS records say it files Form 990 or 990-EZ. Based on its last return; a smaller organization may file the 990-N. Its accounting year ends in June, so each return is due on the 15th day of the 5th month after that.

IRS record

EIN

94-2823247

Tax-exempt status

501(c)(3): Charitable, religious, educational or scientific organization

Foundation status

Publicly supported organization (170(b)(1)(A)(vi))

Donations deductible (Pub 78)

Public charity, 50% deduction limit

Exempt since

1994

Accounting year ends

June

Files

Form 990 or 990-EZ

Category (NTEE)

Philanthropy, voluntarism and grantmaking foundations (T22Z)

Assets (IRS master file)

$49,727,926

Income (IRS master file)

$11,322,675

Filing history

990-N: the IRS bulk file holds only the latest e-Postcard per organization; earlier years come from archived copies of that file since 2020 and can have gaps (the IRS e-Postcard search lists every one). 990, 990-EZ, 990-PF, 990-T: every e-filed return in the IRS e-file index since 2019; XML for the latest three processing years, amounts from the IRS Statistics of Income extracts before that. PDF copies and determination letters at the IRS (search EIN 94-2823247).

Questions about ELKHORN SLOUGH FOUNDATION

What is the EIN of ELKHORN SLOUGH FOUNDATION?

The employer identification number (EIN) of ELKHORN SLOUGH FOUNDATION is 94-2823247.

Is ELKHORN SLOUGH FOUNDATION tax-exempt?

Yes. The IRS lists it as tax-exempt under section 501(c)(3) since 1994.

Are donations to ELKHORN SLOUGH FOUNDATION tax-deductible?

Yes. It is listed in IRS Publication 78 (Public charity, 50% deduction limit).

Which annual return does ELKHORN SLOUGH FOUNDATION file?

Form 990 or 990-EZ. Based on its last return; a smaller organization may file the 990-N.

When is the next return of ELKHORN SLOUGH FOUNDATION due?

The return for tax year 2025 (the year ending June 30, 2026) is due November 16, 2026. Form 8868 extends it by six months; the 990-N cannot be extended.

When did ELKHORN SLOUGH FOUNDATION last file with the IRS?

The latest return in the IRS public files is the 990 for the year ended June 2025.

Who is the principal officer of ELKHORN SLOUGH FOUNDATION?

The 990 for the year ended June 30, 2025 names Mark Silberstein.

Who are the officers and directors of ELKHORN SLOUGH FOUNDATION?

The 990 for the year ended June 30, 2025 lists 19 people; 4 received compensation from the organization, the highest $173,727 (Mark Silberstein, Executive Director).

How much revenue does ELKHORN SLOUGH FOUNDATION have?

On its 990 for the year ended June 30, 2025 it reported revenue of $8,549,320, expenses of $5,853,417 and total assets of $49,727,926 at year end.

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