Tetra Tech, AECOM, WSP and Jacobs still dominate US E&S consulting

The four biggest firms by environmental and sustainability (E&S) consulting revenue in the US – Tetra Tech, AECOM, WSP and Jacobs – made up over 40% of the total US E&S consulting market in 2024.

But this is down 2.0% points on 2023 and has grown only 1.3% points since 2021. Is US market consolidation on pause? 

Check out the US Environmental & Sustainability Consulting Market Assessment: March 2026 Edition to get the full picture. 


 


The Big Four 

More than $25bn of E&S consulting revenue was generated in the US in 2024, with steady growth forecast out to 2029. Four firms took disproportionate shares – more than half of the absolute revenue growth among the largest 29 firms since 2021 came from the Big Four. 

Tetra Tech, on the top spot in 2024, holds the largest share of the total US E&S consulting market. The company has been within the top three by revenue in the US since 2019. Water-related services made up over half of the consultancy’s E&S consulting revenue in the US in 2024.  

Large defence contracts, especially with the US Army Corps of Engineers (USACE), add to this – almost half of the firm’s US E&S consulting revenue comes from federal government clients. Both have strong growth prospects.  

AECOM’s market share also increased to double digits. Government and regulator clients brought in over 40% of the company’s E&S consulting revenue in 2024. 

WSP’s market share stayed steady in 2024 following its rapid expansion in the US from 2019-2023. Acquiring POWER Engineers in 2024 has aided WSP’s rapid rise in the US. 

And in December 2025, WSP announced it was to acquire TRC Companies, which will likely significantly grow its share of the US E&S market, following the deal’s completion in February.  

In turn this will likely increase the Big Four’s share – in 2024 TRC Companies was the fifth biggest company by US E&S revenue. 

Crucially, Jacobs’ position dropped in 2024 after it completed the sale of its Critical Missions Solutions business. This change in market share accounts for 2.4% of the decrease among the Big Four – the three largest firms grew their collective share in 2024. 


 


More moderate M&A activity part of plateau 

A Harvard Business Review article published in 2002, ‘The Consolidation Curve’, introduced the idea that industries move predictably through four stages of consolidation. With time, three firms will typically occupy over 70% market share, it says. 

When the three largest players hold between around 15% and 40%, an industry is said to be in the ‘Scale’ phase. This is characterised by a race to secure market share, more M&A activity and faster consolidation. 

The three largest US E&S consulting players held a combined 31% of the market in 2024. 

But contrastingly, market consolidation in the US has plateaued since 2022, due in part to more moderate M&A activity after a very strong 2021 and 2022 – the Big Four’s market share climbed more than 7% points between 2020 and 2022. 

For instance, Stantec acquired Cardno in 2021. That year, the target brought in some $38m in E&S consulting revenue in the US, predominantly through impact assessment services.

In 2022, WSP acquired Wood’s environment and infrastructure business, which generated $482m in US E&S consulting revenue in 2021. This enhanced WSP’s offering across the spectrum of services, from climate resilience, to impact assessment. 

Also in 2022, Tetra Tech acquired UK-headquartered RPS Group, with $47m in US E&S consulting revenues in 2021. This deal has strengthened Tetra Tech’s offerings in climate change and energy, and EHS, contributing to the acquiror’s journey to top spot among US E&S consulting players. 

As with any other, the E&S consulting-related M&A market is cyclical, and more moderate total revenues acquired since the peak in 2021 and 2022 contribute to the sector’s consolidation plateauing recently.  

Borrowing costs have risen from very low levels during the Covid-19 pandemic, and large firms that made significant acquisitions in the last few years are still integrating target companies into their operations.  

However, the US market remains highly fragmented. There are abundant opportunities for companies of all sizes, especially larger consultancies looking to scale and meet rising demand for integrated services. Strategic partnerships are helping firms expand capabilities, address workforce shortages and advance in tech solutions, fuelling further consolidation.  

WSP’s acquisition of TRC Companies, announced in December 2025 and completed in February, shows there is still appetite for major acquisitions in the US market and will contribute significantly to industry consolidation.  

Combining the two companies’ E&S consulting market shares from 2024 would have given WSP a far more dominant market position.  


 


Check out the US Environmental & Sustainability Consulting Market Assessment: March 2026 Edition to get the full picture.